OBJECTIVE: To select in vitro fertilization (IVF) patients with a low sperm penetration assay (SPA) value and to determine if the penetration rate, fertilization rate, and the pregnancy rate (PR) can be improved in these patients by treating sperm with refrigeration, calcium ionophore A23187, prostaglandin E1, prostaglandin E2, or heparin. DESIGN: The study consists of three parts: identification of patients with poor SPA values, analysis of treatments to improve the SPA value, and evaluation of the treatments to improve fertilization and PRs. RESULTS: The data indicate that treatment of sperm with refrigeration can improve fertilization and PRs during IVF in selected patients previously shown to have an improved SPA value with the treatment. CONCLUSIONS: Three points are emphasized: (1) the treatments analyzed in this study can improve SPA values in some of the patients with low sperm penetration capacity; (2) of the treatments studied, sperm refrigeration resulted in the largest improvement in sperm penetration capacity; and (3) sperm refrigeration can increase fertilization and PRs during IVF in this select group of patients.