The tolerance and efficacy of ethyl (Z)-(3-ethyl-4-oxo-5-piperidino-thiazolidin-2-ylidene) acetate (piprozoline, Gö 919, Problin) were investigated in open and controlled clinical trials involving a total of 1545 patients and 1807 courses of therapy. The objective of this paper is to compare the experimental findings, some of which have already been published, with the results of the extensive clinical investigations. Despite the well-known problems associated with obtaining precise data on upper abdominal disorders, the evaluation of the available comprehensive clinical data has shown that probiline possesses definite therapeutic benefits confirming the experimental findings. Individual complaints such as bloating, upper abdominal pressure, meteorism and flatulence, nausea and vomiting, constipation, anorexia, and fat intolerance improved significantly under probiline therapy. Taking all the criteria into consideration, the overall results of the studies with probiline versus placebo in patients with gall-bladder diseases and intestinal disorders have proved that this choleretic substance is of therapeutic benefit. Serum bilirubin and alkaline phosphatase showed a significantly greater tendency to return to normal levels under probiline therapy than with placebo. The majority of conditions treated were of biliary origin. Aside from establishing the drug's therapeutic profile, the data published also show that the rate of side-effects was insignificant.