We have conducted a meta-analysis of 16 placebo-controlled trials of single drug therapy in ulcerative colitis (UC) for both induction (11 trials) and maintenance of remission (five trials). A total of 468 and 343 patients, respectively, was studied. Various clinical criteria of success were analyzed. The Dersimonian-Laird method for meta-analysis was used to calculate the risk difference. Therapeutic advantage, defined as the difference between drug and placebo response, was also determined. Using various criteria of success, single drug therapy for the induction of remission conferred a therapeutic advantage of 37-48% over placebo. In trials for maintenance of remission, the therapeutic advantage at 6 months was 21%, whereas at 12 months the therapeutic advantage rose to 46% because of a decline in placebo responders with time. In conclusion, meta-analysis has established a standard of reference against which future drug trials can be compared. This standard of reference for drug and placebo rates, as well as the corresponding therapeutic advantages, can help determine the relative value of newer agents in the therapy of UC.