The vocabulary size and composition of one group of full-term and three groups of low risk preterm children with different gestational ages (GA) were longitudinally compared at 10, 22 and 30 months of age. Expressive vocabulary development was assessed through the CDI. Cognitive development was also assessed at 22 months (Batelle Developmental Inventory), and data concerning biological and environmental characteristics of the children were also obtained. Growth curve analyses indicated that there were no significant differences in vocabulary size or percentage of word categories among GA groups. Regression analyses showed that word production and cognitive scores measured at 22 months were the main predictors of total vocabulary and word categories at 30 months. Gender, maternal education and GA did not contribute in a significant way to the variance of use of the vocabulary categories or vocabulary size. Therefore, GA does not seem to affect vocabulary development and composition when biomedical complications associated to prematurity are excluded.