BACKGROUND Ovarian hyperstimulation syndrome (OHSS) is a potentially serious complication of ovulation stimulation. Modest vulvar edema is frequently seen in a severe form of OHSS; however, cases of massive bilateral vulvar edema are rare and pathogenesis is uncertain. CASE REPORT We report a 31-year-old patient with massive vulvar edema and severe OHSS after IVF treatment with GnRH antagonist and gonadotropins. Five days after embryo transfer, she was hospitalized because of severe clinical manifestation of OHSS and on the fifth day after admission she developed a massive bilateral vulvar edema. After conventional medical therapy of OHSS, vulvar edema spontaneously resolved. CONCLUSIONS Hypoproteinemia with low oncotic pressure and certain personal tissue characteristics may play the main role in the pathogenesis of massive vulvar edema in OHSS.