The article presents case reports of two women with symptoms of severe ovarian hyperstimulation syndrome (OHSS) after being treated with in-vitro fertilization and embryo transplantation. Enlarged ovaries, pleural effusion and massive ascites were detected in both women. Their treatment involved intravenous fluid therapy with dextran and albumin, while one of them had to undergo ultrafiltration of the ascites. The article also discusses general pathology, diagnosis and treatment of OHSS. INSETS: Case Report 1;Case Report 2.