This study of patients with first trimester miscarriage evaluates whether conservative management is a feasible strategy and assesses the value of colour Doppler ultrasonography for patient selection. After confirmation of the diagnosis by transvaginal sonography all patients were offered the choice of immediate dilatation and curettage or conservative management. The presence of a gestational sac, the occurrence of spontaneous complete miscarriage within 28 days, detectable pulsatile blood flow within the placenta in the presumed region of the intervillous space and post-treatment complications were the main end-points. Out of a total of 108 women recruited, 23 (21.3%) elected to undergo immediate dilatation and curettage and 85 (78.7%) chose conservative management. The treatment groups were similar in age, gestational age, gestational sac diameter, serum concentrations of human chorionic gonadotrophin (HCG) and progesterone, and proportion of patients who had post-treatment complications (12-13%). Of patients in the conservative management group, 71 out of 85 (84%) had a spontaneous, complete abortion, while 37 out of 46 cases (80%) with detectable presumed intervillous pulsatile blood flow had a complete, spontaneous abortion within 1 week; this occurred in 23% of cases with no detectable flow. This suggests that conservative management is a successful approach for many patients with first trimester miscarriage; colour Doppler ultrasonography can be used to select the most suitable patients for this strategy, and thus reduce the need for hospital admission and surgery.