Prior research on school-age children with mental retardation indicates that they are less motivated on tasks than mental-age-matched peers. In this study, mastery motivation on two tasks was compared for 1- and 2-year-old children with motor impairment (n= 25), developmental delay (n= 25), and typical development (n= 25), matched for mental age. The groups did not differ significantly on any measure of mastery motivation. The relative contribution of premature birth, a history of seizure disorders, severity of cognitive delay, and maternal didactic interaction in predicting mastery motivation was examined for toddlers with developmental delay or motor impairment. Maternal didactic interaction added a significant proportion of variance above and beyond other variables in predicting several aspects of mastery motivation in toddlers with developmental disabilities.