A study was conducted to investigate learner control of instruction in contrast to response sensitive branching algorithms with respect to two specific types of instructional decisions: (1) whether a student should enter and study a particular instructional module given his score on an associated diagnostic pretest; and (2) when a student should terminate practice on each of the problems associated with a concept or principle in an instructional module. It was hypothesized that students given control over the number of modules studied would select fewer modules and that given learner control over tests, students with learner control in instruction would select more modules for study than would students under program controlled instruction. The context of the experiment was a computer-assisted program in precalculus mathematics called "Math-S". Two topics of the program: exponents and dimensional analysis, were covered. The program was run on an IBM Instructional System. Complete data was collected on 97 college physics students. The complete experiment constituted a 2 x 2 design: learner control and program control in diagnostic tests, and learner and program control in the instructional modules. All subjects were administered a pretest and a posttest. Pretest score did not interact with the diagnostic test variable in either exponents or dimensional analysis. Posttest scores were found to be insensitive to diagnostic test variable. No interactions with pretest scores found in either exponents or dimensional analysis. It is concluded that while learner control may well have a facilitative role in computer assisted instruction, further research is required to define the characteristics and limitations of that role. (CK)