Objective: To compare the efficacy of nifedipine with nitroglycerine when used in preterm labor or pregnancy prolongation. Methodology: This randomized control trial was conducted in the department of Gynecology and Obstetrics, Services Institute of Medical Sciences, Lahore, Pakistan from August 2016 to January 2017and None probably consecutive sampling technique was used. Patients were divided into two groups; group N (nifedepine) and group NG (nitroglycerine). Blinding was done by lottery method. The main outcome variable of our study was efficacy of drug.Data were analyzed through SPSS version 23. Results: A total 72 females were included in the study. The mean age and gestational age of the patients was 25.36±3.8years and 32.09±1.78 weeks. Efficacy of drug used in group N was 88.9% and in group NG, efficacy was 61.1%. In group N, prolongation of pregnancy for 48 hours seen in 88.9% patients while in group NG this frequency was 61.1%.Conclusion: Nifedipine was a better tocolytic agent than nitroglycerin for the preterm patients when used for pregnancy prolongation. (Rawal Med J 201;43:280-284). Keywords: Nifedipine, nitroglycerine, preterm labor, tocolytic agent.