Group assertion training has employed a variety of techniques including bibliotherapy, behavioral rehearsal, and didactic lecture presentations. Whether didactic information affects behavior, structure, and/or self-evaluation is unknown, and it is not clear whether behavioral practice enhances the effects of didactic training upon behavior, structure, and self-affect of trainees. Male (N=7) and female (N=21) undergraduates (14 recruits and 14 volunteers) participated in five weeks of group assertion training to investigate the effectiveness of didactic versus rehearsal techniques. The subjects were divided into two treatment conditions: a didactic and a didactic plus rehearsal group. Measures of personality structure, behavior, and self-rated affect revealed that trainees improved in assertiveness and self-rated affect, demonstrated no changes in neuroticism, and exhibited negative changes in both extroversion and defensiveness. Results also revealed that didactic training alone was almost as effective as didactic and rehearsal training combined. The recruits were less assertive but more socially poised than volunteers for assertion training, suggesting that generalizations from recruit populations to volunteer clients should be made with caution. (Author)