This study examined the relationships between habitual physical activity and self-referent thought among Native and non-Native grade 9 students in Southern Ontario. The Habitual Activity Estimation Scale (HAES) and the Children's Self-perception of Adequacy in and Predilection for Physical Activity (CSAPPA) scale were administered to 74% of eligible native students (13M, 13F) and 87% of eligible non-Native students (65M, 65F). All were attending the same secondary school, adjacent to the Six Nations (Mohawk/Cayuga) reservation. Natives and non-Natives differed (P < .01) with respect to physical activity levels, predilection for physical activity, and enjoyment of physical education, with Native students reporting less physical activity than the non-Native group. There were no significant differences in perceived adequacy between the two groups. Further investigations are needed to determine how far these results can be generalized to less prosperous Native bands in other parts of Canada and the U.S. Nevertheless, it appears that physical educators should develop culturally appropriate interventions to increase physical activity among Native youth, in consultation with Native leadership. Am. J. Hum. Biol. 10:629-635, 1998. © 1998 Wiley-Liss, Inc.