Ethyl (Z)-(3-methyl-4-oxo-5-piperidino-thiazolidin-2-ylidene)acetate (etozolin, Gö 687, Elkapin) is a diuretic with a new chemical structure. Animal experiments with etozolin showed low toxicity, potent diuretic and saluretic properties with a mild onset of action. A marked antihypertensive effect was found in long-term experiments in hypertensive rats. In investigations concerning general pharmacology etozolin showed no effects which stand against its use as a diuretic.