N,N-Diethyl-N-(2-[alpha(tricyclo[2,2,1,0(2,6]hept-3-ylidene)-benzyloxy]-ethyl)amine hydrochloride (treptilamine) which in experiments on animals showed distinct spasmolytic effects, has been investigated first in 6 volunteers with regard to compatibility using different doses p.o. and i.v. In connection with this previous study a double blind study including placebo was performed for verification of the observed effects. In the plot study 30, 40 and 50 mg were applied orally and 10, 15 and 20 mg treptilamine were used i.v. The double blind study was designed for 20 volunteers at dosages of 40 mg p.o. and 15 mg i.v. against placebo. In the pilot study systolic blood pressure decreased significantly 5 to 15 min after i.v. application of the substance for 5 or 30 min. The range of accommodation was restricted depending on the dose used. No alteration of circulation was observed after oral application at any dose. All volunteers felt tired. A significant decrease of systolic blood pressure (15 mmHg for 10 min immediately after application) occurred after 15 mg of substance were applied i.v. in the double blind study. No effect on circulation could be seen after placebo. The range of accommodation was restricted in a significant way both after i.v. application (40%) and after oral application (30%). Two of five volunteers recorded a burning sensation in the venous wall which was followed by drowsiness. One volunteer felt increasingly tired after oral application. No influence of the substance could be seen on the clinicochemical parameters examined.