Rothbart (1981) describes the development of a caregiver-report instrument to assess infant temperament and reports longitudinal findings. Temperament dimensions were selected from the work of Thomas, Chess, Escalona, Diamond, and others. Conceptual analysis of scale definitions was conducted to eliminate conceptual overlap, and item analysis was performed on 463 Infant Behavior Questionnaires completed by parents of 3-, 6-, 9-, and 12-month-old infants. Scales with adequate psychometric and conceptual properties were developed for activity level, soothability, fear, distress to limitations, smiling and laughter, and duration of orienting. Longitudinal analyses showed stability in activity level and smiling and laughter from 3 to 12 months, while duration of orienting and soothability showed less stability, and fear and distress to limitations showed stability only beyond 6 months. Temperament, defined as individual differences in reactivity and self-regulation, has a constitutional basis influenced by heredity, life experience, and maturation. Parent reports are useful for assessing infant temperament as seen in the home, but they may not be independent of the child's environment. The Thomas et al. (1963) study was the first large-scale assessment of infant temperament via parent report, identifying key temperament characteristics. However, their results have limitations, including potential homogeneity within scales and age-related confounding. Several parent-report instruments have been developed, including the Infant Characteristics Questionnaire by Bates et al. (1979), which showed moderate internal consistency. The study described here aimed to develop a psychometrically adequate instrument measuring Thomas, Chess et al. (1963, 1968) dimensions and other aspects of reactivity and self-regulation. Eleven temperament dimensions were selected, including activity level, fear, distress to limitations, soothability, duration of orienting, and others. The Infant Behavior Questionnaire was developed through conceptual and item analysis, resulting in six scales: activity level, smiling and laughter, fear, distress to limitations, soothability, and duration of orienting. The study found that these scales had adequate psychometric properties. Longitudinal analyses showed stability in activity level and smiling and laughter, while other scales showed less stability. Intercorrelations among scale scores indicated some relationships between temperament dimensions, though not strong. The study also found some agreement between two adults reporting on the same infant, suggesting that parent reports may reflect consistent observations. The findings suggest that temperament measures may show stability in home environments, which may not be evident in laboratory settings. Further validation studies are needed to confirm these findings.Rothbart (1981) describes the development of a caregiver-report instrument to assess infant temperament and reports longitudinal findings. Temperament dimensions were selected from the work of Thomas, Chess, Escalona, Diamond, and others. Conceptual analysis of scale definitions was conducted to eliminate conceptual overlap, and item analysis was performed on 463 Infant Behavior Questionnaires completed by parents of 3-, 6-, 9-, and 12-month-old infants. Scales with adequate psychometric and conceptual properties were developed for activity level, soothability, fear, distress to limitations, smiling and laughter, and duration of orienting. Longitudinal analyses showed stability in activity level and smiling and laughter from 3 to 12 months, while duration of orienting and soothability showed less stability, and fear and distress to limitations showed stability only beyond 6 months. Temperament, defined as individual differences in reactivity and self-regulation, has a constitutional basis influenced by heredity, life experience, and maturation. Parent reports are useful for assessing infant temperament as seen in the home, but they may not be independent of the child's environment. The Thomas et al. (1963) study was the first large-scale assessment of infant temperament via parent report, identifying key temperament characteristics. However, their results have limitations, including potential homogeneity within scales and age-related confounding. Several parent-report instruments have been developed, including the Infant Characteristics Questionnaire by Bates et al. (1979), which showed moderate internal consistency. The study described here aimed to develop a psychometrically adequate instrument measuring Thomas, Chess et al. (1963, 1968) dimensions and other aspects of reactivity and self-regulation. Eleven temperament dimensions were selected, including activity level, fear, distress to limitations, soothability, duration of orienting, and others. The Infant Behavior Questionnaire was developed through conceptual and item analysis, resulting in six scales: activity level, smiling and laughter, fear, distress to limitations, soothability, and duration of orienting. The study found that these scales had adequate psychometric properties. Longitudinal analyses showed stability in activity level and smiling and laughter, while other scales showed less stability. Intercorrelations among scale scores indicated some relationships between temperament dimensions, though not strong. The study also found some agreement between two adults reporting on the same infant, suggesting that parent reports may reflect consistent observations. The findings suggest that temperament measures may show stability in home environments, which may not be evident in laboratory settings. Further validation studies are needed to confirm these findings.