This meta-analysis reviews experimental and quasi-experimental studies on the use of concept maps in learning. A total of 55 studies involving 5,818 participants were analyzed, yielding 67 standardized mean difference effect sizes. Students from Grade 4 to postsecondary levels used concept maps in domains such as science, psychology, statistics, and nursing. Posttests measured recall and transfer. The use of concept maps was associated with increased knowledge retention, with effect sizes ranging from small to large depending on usage and comparison treatments. Significant heterogeneity was found in most subsets. Concept maps are diagrams representing ideas as node-link assemblies, often used in learning and communication. Over the past two decades, there has been significant interest in their instructional use. The number of publications on concept maps, knowledge maps, or node-link maps has greatly expanded since 1985. Over 500 peer-reviewed articles have been published on the educational application of concept or knowledge maps. Graphic organizers are two-dimensional visual representations showing relationships among concepts. They were conceived as an entailment of Ausubel's theory of meaningful learning. Concept maps are a type of graphic organizer with labeled nodes and links. They may be labeled or unlabeled, directional or non-directional. Concept maps have been used for communication and learning since the 13th century. Researchers have investigated various ways of using concept maps. One branch examines student construction or modification of concept maps. Another branch investigates the cognitive effects of studying or communicating with preconstructed maps. Concept maps are effective in interactive software environments. Graphic organizer research is relevant to analyzing the effects of concept maps. Moore and Readence found that initiating learning activities with graphic organizers led to small, positive effects on comprehension. Horton et al. found that concept mapping by students raised posttest achievement scores by a mean of .42 standard deviations. Several explanations have been advanced for the beneficial effects of concept maps. Dual coding theory suggests that concept maps can facilitate learning by incorporating labeled nodes drawn as distinct, mimetic icons. Conjoint retention theory suggests that concept maps may facilitate learning by enabling the learner to code a spatial frame for indexing and efficiently retrieving concepts. Verbal coding suggests that the graphical conventions of concept maps are coded more like texts than pictures. Concept maps may facilitate verbal coding by co-locating concepts that have similar meanings or are subsumed by the same higher-order concept. Learning strategies suggest that concept maps may enhance learning when used to summarize information. Individual differences suggest that low-ability students may obtain greater benefit from instructional diagrams than high-ability learners. Collaborative and cooperative learning suggest that concept maps suit collaborative learning because they make economical use of text and can be written with letters large enough to be viewed by a small group. The meta-analysis addressed several research questions, including the effects of learning activities involving concept maps, the effects of studying maps compared to other materials, and the effects of using maps in different knowledge domains, educational levels, andThis meta-analysis reviews experimental and quasi-experimental studies on the use of concept maps in learning. A total of 55 studies involving 5,818 participants were analyzed, yielding 67 standardized mean difference effect sizes. Students from Grade 4 to postsecondary levels used concept maps in domains such as science, psychology, statistics, and nursing. Posttests measured recall and transfer. The use of concept maps was associated with increased knowledge retention, with effect sizes ranging from small to large depending on usage and comparison treatments. Significant heterogeneity was found in most subsets. Concept maps are diagrams representing ideas as node-link assemblies, often used in learning and communication. Over the past two decades, there has been significant interest in their instructional use. The number of publications on concept maps, knowledge maps, or node-link maps has greatly expanded since 1985. Over 500 peer-reviewed articles have been published on the educational application of concept or knowledge maps. Graphic organizers are two-dimensional visual representations showing relationships among concepts. They were conceived as an entailment of Ausubel's theory of meaningful learning. Concept maps are a type of graphic organizer with labeled nodes and links. They may be labeled or unlabeled, directional or non-directional. Concept maps have been used for communication and learning since the 13th century. Researchers have investigated various ways of using concept maps. One branch examines student construction or modification of concept maps. Another branch investigates the cognitive effects of studying or communicating with preconstructed maps. Concept maps are effective in interactive software environments. Graphic organizer research is relevant to analyzing the effects of concept maps. Moore and Readence found that initiating learning activities with graphic organizers led to small, positive effects on comprehension. Horton et al. found that concept mapping by students raised posttest achievement scores by a mean of .42 standard deviations. Several explanations have been advanced for the beneficial effects of concept maps. Dual coding theory suggests that concept maps can facilitate learning by incorporating labeled nodes drawn as distinct, mimetic icons. Conjoint retention theory suggests that concept maps may facilitate learning by enabling the learner to code a spatial frame for indexing and efficiently retrieving concepts. Verbal coding suggests that the graphical conventions of concept maps are coded more like texts than pictures. Concept maps may facilitate verbal coding by co-locating concepts that have similar meanings or are subsumed by the same higher-order concept. Learning strategies suggest that concept maps may enhance learning when used to summarize information. Individual differences suggest that low-ability students may obtain greater benefit from instructional diagrams than high-ability learners. Collaborative and cooperative learning suggest that concept maps suit collaborative learning because they make economical use of text and can be written with letters large enough to be viewed by a small group. The meta-analysis addressed several research questions, including the effects of learning activities involving concept maps, the effects of studying maps compared to other materials, and the effects of using maps in different knowledge domains, educational levels, and