Several methods for micromanipulation of human gametes have been proposed to enhance fertilization in cases of male infertility. Of these methods, two have been successful in producing pregnancies and live births worldwide; these include partial zona dissection and subzonal sperm insertion. During the period between October 1989 and July 1991, 251 patients with male infertility due to impaired sperm function were treated with in vitro fertilization in conjunction with gamete micromanipulation at our center. Sixty pregnancies (24% per cycle, 42% per replacement) resulted in 144 patients. The details of these treatments are discussed. In another study, in an attempt to increase the incidence of implantation, we have conducted three clinical trials of assisted hatching and selected assisted hatching. The combined results of the trials indicate a clinical pregnancy rate of 51% in the control group and 60% in the micromanipulated group (P less than .05). Moreover, while 20% of the embryos replaced in the control group implanted the implantation rate was increased to 28% in the experimental group (P less than .05). Methodologies and possible implications of these treatments are discussed.