Micromanipulation procedures have been used to improve fertilization rates in patients with male factor or with unexplained infertility. Partial zona disseetion(PZD), a method using mechanical force to open the zona pellucida increase the chances of fertilization. The purpose of this study is to increase rates of fertilization and pregnacy in the ART program by using PZD. The influence of PZD on the fertilization rate was investigated in 57 couples with semen defects, antisperm antibodies(ASA), or unknown factors. PZD directly performed in 35 couples with a history of fertilization failure in previous cycle (Group 1), and PZD applied in 22 couples with the failure of initial fertilization in the same cycle (Group 2). The fertilization rates of the male facor, ASA positive factor and unknown factor in Group 1 were 37.6%, 20.0% and 59.2%, respectively. The rates of fertilization of male factor, ASA positive factor and unknown factor in Group 2 were 34.8%, 20.0% and 26.5%, respectively. The incidences of polyspermy in Group 1 and Group 2 were 5.9% and 9.0%, respectively. Among 35 patients of Group 1, one patient was pregnant and successfully delivered, whereas 1 of 22 patients of Group 2 became pregnant, but aborted at 7 weeks.