This study examined different scheduling demands as a moderator of the self-regulatory efficacy (SRE)/physical activity relationship.A prospective design was used.Adolescents (N=275) reported SRE and activity during times that reflected high and low scheduling demands.When scheduling demands were high, SRE predicted individual activity behavior (p<.001). During a period that reflected lower scheduling demands, however, SRE did not predict physical activity behavior (p=.25).These findings support the idea that the level of challenge (demands) may be an important factor to consider when examining the SRE/activity behavior relationship.