A patient being treated for chronic myeloid leukaemia with hydroxyurea became pregnant. Despite an increase in the dose of hydroxyurea (to 3 g per day) during the pregnancy, her white blood cell count could only be controlled at about 150 x 10(9)/l. A healthy baby girl was born at 37 weeks with normal blood counts and no evidence of congenital abnormality. There are now five reports of the use of hydroxyurea in pregnancy, and where leukapheresis is not available it may be the treatment of choice.