A five-year follow-up of 30 phobics originally identified in a population survey, revealed that untreated phobia tends to improve. Children's phobias improve quickly, 100% being improved or recovered at the end of five years. Adult's phobias improve more slowly, 43% being improved or recovered, 20% unchanged, and 33.0% worse at the end of five years. Severity of the phobia was not predictive of outcome, however degree of generalization of the phobia, and fearfulness, were. High generalization and fearfulness were associated with poor outcome. The similarity of these findings to follow-up studies of treated phobia suggests common mechanisms underlying recovery in both treated and untreated cases. A review of recent findings suggests that exposure to the feared object or situation is the common mechanism.