Forty-nine patients with ureteral colic were included in this prospective double-blind study investigating the analgesic efficacy and side effects of a prostaglandin synthetase inhibitor Diclofenac sodium (Voltaren) versus a spasmolytic drug Tropenzilium bromide (Palerol). The analgesic efficacy and side effects of the calcium antagonist Nifedipine (Nidilat) applied sublingually in ureteral colic were also investigated. It was concluded that diclofenac sodium was more efficient for relieving pain due to acute ureteral obstruction and had fewer side effects than spasmolytic drugs. Nifedipine proved to have an analgesic effect equivalent to that of Tropenzilium bromide.