Abstract A single-center randomized double dummy study was undertaken in 116 patients; 59 were randomized to mesalamine and 57 to receive a nonpathogenic strain of Escherichia coli. In addition, all patients received standard medical therapy, together with a 1-wk course of oral gentamicin. After remission, patients were maintained on either mesalamine or E. coli and observed for a maximum of 12 months. Duration of remission was slightly higher in the mesalamine group than in the E. coli group (206 vs 185 days). Similarly, the percentages of patients undergoing remission were equivalent (73% and 67%), again slightly favoring the mesalamine group. The authors, therefore, conclude that a nonpathogenic strain of E. coli has an effectiveness almost equivalent to mesalamine’s in maintaining remission of ulcerative colitis.