The effect of calcium antagonists nifedipine and verapamil on spontaneous rhythmic contractions of human isolated ureter obtained from donor subjects undergoing kidney transplantation was investigated in comparison with a nonsteroidal antiinflammatory drug indomethacin. Stop-times i.e. the time elapsing from application, were determined for each drug. The rank order of potency at 10(-8) and 10(-7) M concentrations of the drugs was : nifedipine>verapamil greater-than-or-equal-to indomethacin. However, no significant difference of the stop-times was observed at 10(-6) M concentration of the drugs tested. The rhythmic contractions were re-activated by PGF2alpha after stoppage with indomethacin but not with nifedipine or verapamil. These results suggest that not only endogenous PG synthesis but also an influx of calcium from the extracellular space is responsible for the spontaneous rhythmic activity of human ureter. The beneficial effects of using calcium antagonists in the treatment of ureteric colic is discussed.