This study examined the effects of a weekend marathon on the level of self-actualization of college students one and four weeks following their group experience. It also studied the relationship between ego strength and extent of change in self-actualization during a marathon. Generally, the group experience did increase self-actualization and the effects persisted through the fourth week after the group. The possibility of a sleeper effect was discussed, and hypotheses were offered regarding conditions necessary for such groups to be effective. Participants' initial level of ego strength was unrelated to changes in self-actualization. (Author)