The objective of the study was to determine the effect which a unit dealing with recursive definitions would have on students' achievement in applying the principle of mathematical induction (PMI). Twenty-four secondary school students were randomly assigned to control and experimental groups. Students in the control group studied programmed units of the PMI program first and then programmed units on the recursive definition program. This procedure was reversed by the experimental group. Data were obtained from a posttest and a subsequent retention test. A 2 x 2 analysis of variance was used to analyze data. Changes in score were analyzed using "t" tests. The study indicates that it makes little difference whether a unit on recursive definitions precedes or follows a unit on the PMI. (Author/JBW)