['To evaluate two commonly used methods of sperm preparation with respect to their effects on sperm morphology (strict criteria).', 'Auto-controlled, split sample study performed on the semen of 74 male partners of couples enrolled for IVF.', 'In vitro fertilization and andrology laboratories at a tertiary care, major teaching hospital.', 'Seventy-four male partners of couples who were scheduled to undergo IVF.', 'Equal halves of the same semen sample were evaluated for strict criteria sperm morphology before and after preparation by differential gradient centrifugation using Percoll (Pacific Andrology, Montrose, CA) and by the standard swim-up method.', 'The percentage of morphologically normal sperm was assessed using strict criteria before and after the two methods of sperm preparation. Specific parameters studied were individual abnormalities of the head, midpiece, and tail.', 'Sperm preparation using differential gradient centrifugation with Percoll produced a significantly greater number of specimens with normal sperm morphology and also showed higher absolute quantitative improvement over the swim-up method. The two methods were comparable in regard to their effects on specific sperm abnormalities (i.e., head, midpiece, and tail defects).'] Is preparation by differential gradient centrifugation better than swim-up in selecting sperm with normal morphology ( strict criteria )?