This study examined the specific effects of picture and object stimuli on two types of language performance: comprehension and performance. Subjects were 48 4- and 5-year-olds who were randomly assigned to one of four groups. Groups were matched for SES, sex, and age and tested individually with one of the four measures: language comprehension with object stimuli; comprehension with picture stimuli; language production with object stimuli; or production with picture stimuli. Results indicated that: (1) 4- and 5-year-olds showed overall superior performance on object assessment tasks as compared to performance on picture-assessment tasks; (2) language comprehension tasks were performed more accurately than language production tasks by the 4- and 5-year-olds; and (3) an interaction effect occurred between task medium (picture or object) and response type (comprehension or production) so that comprehension and production differences were greater when assessed by pictures than by objects. (Author/SB)