Hyperreactio luteinalis (HL) is a rare condition that is characterized by bilateral ovarian enlargement and multiple thin walled cysts. Hypersensitivity of the ovary to circulating human chorionic gonadotropin (hCG) is playing the main role in pathophysiology. HL observed in cases where there is high serum ß-HCG levels, similarly to gestational trophoblastic disease, multiple pregnancies, hydrops fetalis and after fertiliy treatment. Most of HL are self limiting condition and patients are asymptomatic. Differentiation from ovarian malignancies is important. This is a case report of severe preeclampsia prior to 20 weeks gestation due to hyperreactio luteinalis.