Fifty-nine inservice teachers in grades 1 through 12 took "Minicourse 20: Divergent Thinking," a course training teachers to use brainstorming to stimulate divergent thinking in students. Tapes of brainstorming sessions were made before, after, and seven weeks after the course ended. Experimental teachers improved significantly more than controls in the skills of not evaluating during brainstorming and not making unnecessary comments (e.g., repeating answers) or shaping student ideas (e.g., probing answers). They did not show improvement in the use of techniques such as categorizing to stimulate more divergent brainstorming. Teaching skills were acquired equally well by teachers who mocrotaught with audiotape feedback and by those who microtaught with videotape feedback. Control teachers showed no gains in teaching skills. Brainstorming responses given by students of the teachers were analyzed. Elementary students showed significantly greater gains in fluency, flexibility, and originality than the control group. The secondary sample did not improve. There were no significant differences between experimental and control groups on the Torrance Tests of Creative Thinking given before and seven weeks after the course. (Author)