Several experiments have reported that observing another person receiving reinforcement may sometimes have motivational effects upon the observer. The results of these studies, however, are confounded by two factors ; namely, the effects of vicarious reinforcement, and by models' performance speeds. The main purpose of the present study was to determine the relative importance of vicarious reinforcement and the observation of models' response speeds on a simple motor task with preschool children. Sixty preschool children, 36 boys and 24 girls, served as subjects. These children were randomly assigned to one of six subgroups of a 2 X 3 experimental design which involved two vicarious reinforcement conditions and three demonstrational response speeds by models. In the first phase of the experiment, subjects individually observed a female adult model performing a marble-dropping task. Depending on the subjects' assigned conditions, the trained model dropped one of the following numbers of marbles per minute : 1) 36 marbles, 2) 24 marbles, or 3) 15 marbles. During this observation, one-half of the subjects observed the model receiving positive social reinforcement (praise) while working on the task. The other half of the subjects observed the model who was not receiving social reinforcement. After watching the models perform for four minutes, the observer children worked on the same task for five minutes without direct social reinforcement. The number of marbles dropped through holes by the subjects per minute was used as the dependent measure. The results of the study strongly indicate that the models' performance speeds have positive effects on the observers' subsequent performance. Those children who observed models working at a faster speed dropped significantly more marbles than those children who observed models working at a slower speed. On the other hand, the effects of vicarious reinforcement on children's response rate were not noted under any demonstrational conditions.