Objectives: The pain assocaited with ureteralobstruction is caused by a rise in intraluminalpressure above the obstruction which producesan increase in tension of the ureteral smoothmuscle. A reduction in pressure will result indecreased tension and relief of pain. In thisstudy we used papaverine and a prostaglandinsynthesis inhibitor, diclofenac sodium todecrease ureteral tension and compaired theireffects on isolated human ureteric smoothmuscle.Materials and methods: Experiment havebeen carried out with isolated ring preparationof human ureter. The tissue displayedspontaneous activity and contracted whenexposed to KCI (40 mM). Papaverine(10−5 M) and diclofenac sodium(10−8–10−5 M) were applied on theprecontracted segments and isometric variationwas recorded with Nihon-Kohden TB-612 isometrictransducer. Their relaxant responses werecomparatively examined.Results: Mean relaxation obtained bydiclofenac sodium and papaverine wererespectively 43.19% and 28.96%. Our studyshowed that diclofenac sodium may be morepotent than papaverine in the treatment ofrenal colic.