This study examines the course of emotion expression development over the first 2 years of life in a sample of full-term and preterm children. 58 mother/infant pairs were videotaped at infant ages of 2 1/2, 5, 7 1/2, and 22 months, recording face-to-face interaction involving play and separation/reunion sessions. The tapes were coded on a second-to-second basis using Izard's facial affect coding system. Data analysis focused on (1) differences in expressive behavior at 22 months as a function of risk status, gender, attachment status, and patterns of earlier maternal contingency behavior; (2) stability of specific emotional expressive patterns across assessment periods; and (3) the relation of expressive behavior and security of attachment at 2 years to qualities of earlier affective interchange. Mother's contingency behavior (both general level and specific contingency patterns) appeared to have a material effect on the course of emotional development, as did birth status and gender. Prematurity was associated with differential socioemotional development well into the second year, much in contrast to the "catch-up effect" observed in linguistic and cognitive functioning. Discrete emotions analysis of attachment groups yielded differentiation along a broad negative/positive dimension, but it also showed that insecurely attached children can be characterized as showing inhibited anger expression. The results of this study are discussed within the framework of organizational models of infant affective development; attachment theory and discrete emotions approaches were found to yield different yet equally informative data on the course of socioemotional development.