Depressed patients who had responded to either cognitive therapy, pharmacotherapy or the 2 treatments combined, were followed up retrospectively over a period of 2 years. There were significantly more relapses at 6 months in the pharmacotherapy group compared to the combined treatment group and the 2 cognitive therapy groups together. The number of individuals who relapsed at some point over the 2 years was significantly higher in the pharmacotherapy group than in either of the cognitive therapy groups. When hospital patients were considered separately, significantly more patients in the pharmacotherapy group relapsed over the 2 years compared to the 2 cognitive therapy groups combined. Methodological problems of naturalistic follow-up studies are discussed and the prophylactic potential of cognitive therapy is discussed relative to continuation drug treatment.