In subsequent studies 300 mg of proxyphylline (Group 1) and 1 amp Baralgin (Group 2) were administered intravenously to 20 patients in order to study the relaxing effect of proxyphylline and Baralgin on the contracted gallbladder in connection with routine oral cholecystography. After the standard contraction meal (200 ml cream) the intravenously administered proxyphylline had no relaxing effect on the human gallbladder, whereas Baralgin caused a significant dilation. The dilation effect lasted throughout the whole study period (60 min). Proxyphylline concentrations in the serum, determined by gas-liquid chromatography, proved to be on the therapeutic level which is said to be effective in the treatment of obstructive pulmonary disease. Because with proxyphylline no dilation effect on the gallbladder was found, the clinical spasmolytic response to proxyphylline during an acute attack of pain in a patient suffering from gallstones seems to be questionable. Baralgin caused a significant dilation effect on the gallbladder, and it seems to be a useful agent in an acute gallstone attack.