A single dose of 10 mg of pirenzepine given i.m. to 7 healthy volunteers did not elicit local or general signs of intolerance within 6 hours after injection. We also found no significant differences in tests of vegetative symptomatology, visual motor coordination, attention concentration, critical flicker test threshold, nor any other aspects of the central nervous or cardiovascular systems. Ten patients with ulcers receiving pirenzepine 25 mg twice daily also showed no significant changes in psychometric tests, neurotic symptomatology, anxiety, depressive signs and clinical state during 4 weeks treatment. Side-effects of the anticholinergic type occurred only after high doses.