This article presents a systematic review of the literature on self-monitoring in behavioral weight loss programs, focusing on three components: diet, exercise, and self-weighing. The review includes 22 studies published between 1993 and 2009, with 14 studies on dietary self-monitoring, one on exercise self-monitoring, and six on self-weighing. Paper diaries were the most commonly used method, and adherence was often measured by the number of completed diaries or frequency of log-ins/weights. Technology, including the Internet, personal digital assistants (PDAs), and electronic scales, was used in five studies. Early studies used descriptive designs, while more recent reports involved prospective studies and randomized trials. A significant association between self-monitoring and weight loss was found, but the evidence was weak due to methodological limitations, such as homogeneous samples and reliance on self-report. The review highlights the need for studies in diverse populations, objective measures of adherence, and establishing the optimal dose of self-monitoring for successful outcomes.This article presents a systematic review of the literature on self-monitoring in behavioral weight loss programs, focusing on three components: diet, exercise, and self-weighing. The review includes 22 studies published between 1993 and 2009, with 14 studies on dietary self-monitoring, one on exercise self-monitoring, and six on self-weighing. Paper diaries were the most commonly used method, and adherence was often measured by the number of completed diaries or frequency of log-ins/weights. Technology, including the Internet, personal digital assistants (PDAs), and electronic scales, was used in five studies. Early studies used descriptive designs, while more recent reports involved prospective studies and randomized trials. A significant association between self-monitoring and weight loss was found, but the evidence was weak due to methodological limitations, such as homogeneous samples and reliance on self-report. The review highlights the need for studies in diverse populations, objective measures of adherence, and establishing the optimal dose of self-monitoring for successful outcomes.