A study is reported in which the effects of 2 competitive treatments on mean classroom performance, interest and retention were examined with the use of a 10-day vocabulary-learning task. Sixty-six 5th grade classrooms were randomly assigned to one of 3 conditions: (1) control; (2) competition with reward; and (3) competition in a game setting. The results indicate that, contrary to prediction, neither performance nor retention was increased under the competitive treatments. However, interest was found to be significantly higher in these treatments than in the control. Finally, and according to prediction, little variability was found between the effects of the 2 competitive conditions on the 3 dependent variables. A model relating task-complexity and motivation to increased performance is proposed and discussed. Several related areas of educational research are suggested, all of which concern aspects of cognitive and affective motivation. (Author/TL)