This document reports an experiment designed to assess the effects of learner control over the level of challenge in computer-assisted instruction (CAI) and collect data that will guide the design of future learner control experiments. The subjects were 78 undergraduate students in the College of Education at a large public university. The CAI included a simulation of an aviation instrument and taught subjects how to locate an aircraft's position in space by interpreting a complex display. Instructional research has not yielded the empirical information necessary to develop prescriptions for employing learner control features in this type of CAI. Three treatments that varied the subject's control over the level of challenge were compared: learner control, computer control, and learner control with advisement. Results indicated that learner control did affect subjects' time on task on an immediate test, but this effect appeared to be temporary. The change in time on task was probably caused by the way subjects adjusted their challenge level. Subjects who received advisement tended to set challenge levels higher and adjusted the challenge more frequently. One table and three figures are appended. (12 references) (Author/BBM)