['To test whether pentoxifylline, a drug previously shown to sensitize spermatozoa from normal samples to the action of acrosome reaction stimuli, can be used to improve the fertilizing ability of spermatozoa from patients with acrosome reaction insufficiency.', 'Prospective analysis of pentoxifylline effects on the acrosome reaction and zona-free egg penetration; retrospective comparison of IVF results with and without the use of pentoxifylline.', 'Private hospital, public research center, and university-based laboratory.', 'In vitro fertilization patients selected on the basis of a previous acrosome reaction test.', 'None in the experimental part; IVF-ET in the clinical part of this study.', 'Frequency of the acrosome reaction, rate of penetration of zona-free eggs, normal fertilization in IVF attempts.', 'Pentoxifylline improves the acrosome reaction scores and zona-free egg penetration rates in patients with acrosome reaction insufficiency. Preliminary clinical experience shows an improvement of IVF results in these patients.'] Does sperm treatment with pentoxifylline improve the fertilizing ability in patients with acrosome reaction insufficiency?