Objective: To determine the efficacy of TV albumin in the prevention of severe ovarian hyperstimulation syndrome (OHSS). Design: Prospective study group with historical control. Setting: University hospital-based IVF program. Patient(s): Between 1993 and 1995, 42 consecutive patients undergoing IVF-ET or tubal ET who had serum E-2 levels greater than or equal to 3,600 pg/mL (conversion factor to SI unit, 3.671) on the day of hCG administration and/or greater than or equal to 20 oocytes retrieved were considered at high risk for severe OHSS and were selected as the control group. From December 1995 to October 1996, IV albumin was given to 30 consecutive patients who fulfilled these criteria. Intervention(s): The treatment group received TV albumin after oocyte retrieval. Main Outcome Measure: Occurrence of severe OHSS. Result(s): None of the 16 patients in the treatment group in nonconception cycles developed severe OHSS, compared with 5 (21.7%) of 23 in the control group. In conception cycles, 4 (28.6%) of 14 patients in the treatment group developed severe OHSS, compared with 9 (47.4%) of 19 in the control group. All 4 patients with multiple pregnancies in the treatment group developed singleton pregnancies in the treatment group developed severe OHSS, compared with 6 (42.9%) of 14 in the control group. Conclusion(s): Intravenous albumin prevents severe OHSS in high-risk patients who did not conceive or who carried singleton pregnancies, but not in the patients with high-order pregnancies. (C) 1997 by American Society for Reproductive Medicine.