The present investigation was designed to examine the effects of the positive manipulation of information on self-efficacy and subsequent performance of 180 female subjects. High, moderate, and low self-efficacy subjects were randomly assigned to a treatment condition in a 3 x 4 x 3 (preexisting self-efficacy x efficacy information source x trials) factorial design. Information from the three efficacy sources of performance accomplishments, verbal persuasion, and vicarious experience was manipulated towards success after subjects completed a muscular leg endurance task. The results supported self-efficacy theory with high self-efficacy subjects extending their legs significantly longer than moderate and low self-efficacy subjects. However, subjects did not differentially [sic] respond to the manipulation of the efficacy information. Results are discussed in terms of efficacy as a mediator of performance on an endurance task as well as the lack of differential changes in efficacy based on the source from which that information is derived.