The present study investigated the effects of locus of control and differential instructions on speech performance under delayed auditory feedback (DAF). It was hypothesized that internals would perform better under skill instructions than under chance instructions, and conversely, that externals would perform better under chance instructions than under skill instructions. In a 2x2x2 design, internal and external Ss received either skill or chance instructions prior to performing under DAF. The results indicated that Internal-males under skill instructions made fewer speech errors than Internal-males under chance instructions and that External-females under chance instructions made fewer speech errors than External-females under skill instructions. It was also demonstrated that internal Ss take less time to complete the DAF task under skill instructions than under chance instructions. Thus the hypothesis was only partially confirmed. The results were interpreted in terms of Rotter and Mulry's (1965) theory which attributed better performance to motivational factors; Watson and Baumal's (1968) theory which attributed poorer performance to anxiety; and to an additional factor defined as an active-passive dimension.