This study investigated the effects of Guided Discovery vs. Didactic methods of instruction upon the acquisition of certain inquiry skills. At the same time, the effects of method on the attainment of factual-conceptual achievement was assessed. Hypotheses of no interaction of the methods variable with the learner variables—sex, measured intelligence, creativity, interest in science, general scholastic achievement, and science achievement—were also tested. The sample consisted of 140 8th-grade students. The duration of the experimental unit was six weeks. The subject matter was the same for each, “Early Man in America.” The results favored the Didactic group for the factual-conceptual achievement and the Guided Discovery for the acquisition of inquiry skills. However, in the latter there was an interaction of method with levels of measured intelligence and achievement.