Developing self-restraint, or the inhibition of behavior in response to a prohibition, is an important process during toddlerhood. The objective of this study was to gain a better understanding of individual differences in the development of self-restraint during toddlerhood by examining stable elements and growth of temperament (i.e., attentional control, behavioral inhibition, negative emotionality), general intelligence, and self-restraint. Participants were 412 same-sex twin pairs (approximately 90% European American) from predominately middle-class households in Colorado. Data were collected at 14, 20, 24, and 36 months. Results indicated that higher behavioral inhibition, attentional control, and intelligence were independently associated with better self-restraint, whereas higher negative emotionality was an independent predictor of lower self-restraint. The associations between temperament and self-restraint generally appeared to be stable from 14 to 36 months. [ABSTRACT FROM AUTHOR]