There are few studies of behavior problems in preterm children prior to 2 years old and the changes that occur over time. The aims of this study were to examine the patterns and prediction of behavior problems and the effects of gender and socioeconomic status (SES) on behavior problems in preterm children at the toddler and preschool periods. Parents of 124 very low birthweight preterm children completed a standardized behavior questionnaire at 18 months corrected age and 3 years old. At both times, scores were significantly higher on Attention and Withdrawn Problems than on other behavior problem syndromes. There was a significant overall increase in Externalizing and Internalizing behavior problem scores between 18 months and 3 years, particularly in Internalizing problems. Overall prediction for normal versus not-normal categorization ([greater than or equal to]1 standard deviation) on behavior problem and broad-spectrum scales ranged from 77% to 90% and was higher for children in the normal than not-normal categories. Boys had higher Internalizing Problems at 18 months and higher Externalizing Problems at 3 years. Children from low SES families had higher Internalizing and Total Behavior problems at 18 months and higher Internalizing, Externalizing, and Total Behavior problems at 3 years. Screening preterm children for behavior problems before 2 years old appears useful for early intervention of such problems.