Comparative clinical trials were conducted by the double-blind technique in a series of 302 cases of gastric ulcer at fifteen medical institutions in order to investigate the clinical course of peptic ulceration and the effect of pharmacotherapy on it, using N-acetyl-L-glutamine aluminum complex (KW) as test drug and basic aluminum sucrose sulfate (UL) as reference drug as well as an inactive placebo of lactose (PL) with the results as follows: In 12 weeks of treatment with inactive placebo, a higher cure rates were noted in inpatients than in outpatients, and in patients with ulceration in the corpus ventriculi than in those with ulceration at the angulus. The overall evaluation of therapeutic responses indicated that, both KW and UL were significantly superior in efficacy to placebo in 12 weeks of therapy. These two medicaments displayed different modes of efficacy, possibly reflecting their different mechanisms of pharmacologic action. The efficacy of the medicaments was particularly superior in outpatients and patients with peptic ulceration at the gastric angle both of which showed lower rates of response to placebo.