Abstract
Early malignant disease of the chorion recognised within a month of hydatidiform mole occurred in 9.6% of 532 molar pregnancies. Malay patients and patients above 40 years showed an increased risk of malignancy. The local and metastatic features of the disease are described. A secondary rise in serum HCG is typical. Treatment of choice is methotrexate. The overall mortality is 3.9%.