The aim of the study was to examine the impact of a self-determined motivational climate including support of autonomy, relatedness, task involvement, and ego-involving climate on students' affective responses and effort in physical education. The sample involved 338 sixth-grade students (11-12 years old) who completed a questionnaire battery incorporating measures of motivational climate, enjoyment, trait anxiety in physical education, and effort. The results of the reliability and confirmatory factor analyses supported the psychometric properties of the measures. Multiple regression path analysis results indicated that task-involving climate, autonomy, and relatedness support had more positive influences on pupils' affective responses in comparison to an ego-involving climate. (Contains 2 tables and 2 figures.)