A 28 year old patient with primary thrombocythaemia, who had had two stillbirths in the third trimester, is reported. She was successfully treated with hydroxyurea and delivered a healthy 6lb boy by elective caesarean section. The ease with which this treatment can be given, its high level of tolerance among patients, and its low cost are Likely to increase its use as a safe and effective treatment in pregnant patients with primary thrombocythaemia.