Objective:To review studies and investigations regarding the safety and efficacy of nifedipine.Data sources and methods:We reviewed the published literature on calcium channel blockers and their pharmacology and therapeutic applications in obstetrics and gynecology. We paid particular attention to methods of animal research and recent clinical evaluations.Conclusions:The dihydropyridine group of calcium channel blockers (type II calcium blockers) and, specifically, nifedipine are safe for use in pregnancy. They have little teratogenic or fetotoxic potential. Nifedipine's mechanism of action is through smooth‐muscle relaxation secondary to blockage of the slow calcium channels into the cells. In vivo, there is minimal effect on the cardiac conducting system. Multiple studies in women have demonstrated the effectiveness and safety of nifedipine as an antihypertensive. Therapeutic doses range from 10‐30 mg orally every 6‐8 hours. For acute control of hypertension, 10 mg of sublingual nifedipine may be used. Nifedipine is as effective as betamimetics in decreasing uterine activity. As a tocolytic agent, it is more effective as there are fewer patients who have to discontinue nifedipine because of side effects. The side effects of nifedipine include flushing, headache, or, rarely, hypotension in the hypovolemic patient. Nifedipine has potential and theoretical indications for dysmenorrhea and bladder irritability.(Obstet Gynecol 1994;83:616‐24)