OBJECTIVE: To compare sperm preparation with a new self-migration method in sodium hyaluronate and a centrifugation/swim-up method and to study the efficiency of direct intraperitoneal (IP) insemination. STUDY DESIGN: Sodium hyaluronate and centrifugation/swim-up were used randomly for direct IP insemination in alternating cycles. Treatments were given with an interval of at least one untreated cycle. When ovulation occurred on weekends, the patients received only controlled ovarian hyperstimulation. SETTINGS: Department of Obstetrics and Gynecology University Hospital, Uppsala, Sweden. PATIENTS: Seventy-nine couples with unexplained infertility (n = 53), endometriosis (n = 17), and cervical factor (n = 9). INTERVENTIONS: Controlled ovarian hyperstimulation was accomplished by clomiphene citrate and gonadotropins. MAIN OUTCOME MEASURES: Sperm parameters and pregnancy rates. RESULTS: Sodium hyaluronate and centrifugation/swim-up resulted in similar conception rates, but sodium hyaluronate recovered more motile spermatozoa than centrifugation/swim-up (P less than 0.0001). The number of patients who became pregnant after direct IP insemination or controlled ovarian hyperstimulation only was significantly higher than that observed after untreated cycles (P = 0.00001 and P = 0.008, respectively). CONCLUSIONS: Sperm preparation with sodium hyaluronate can be used as an alternative to centrifugation/swim-up. Direct IP insemination appears to increase the cycle fecundity, but whether direct IP insemination/controlled ovarian hyperstimulation is more effective than controlled ovarian hyperstimulation alone has yet to be proven.