This study seeks to identify factors that promote positive experiences in high school physical education (PE). The study combines elements of Self-determination Theory (SDT) with the theory of flow. Special attention is given to gender differences. The study sample consisted of 167 Norwegian senior high school students (78 females and 89 males) who completed a questionnaire after having participated in a PE class. The majority of the students reported having flow experiences, although this was more true for boys than for girls. Those who had experienced flow also tended to be those who had experienced the fulfilment of basic psychological needs and were characterized by a high level of autonomous motivation. In boys, the need for competence was a stronger predictor of flow than other factors, while for girls the need for relatedness was the stronger predictor of flow. Although a high percentage of the participants in this study reported an experience of flow, a significant minority of the students (more girls than boys) did not report an experience of flow. The findings confirm previous research on the relationship between the different constructs of SDT and the experience of flow, indicating that this relationship also applies in PE. The experience of flow in PE might result in positive PE experiences that can have significant health benefits for the individual student and our society.