To compare the efficacy and complications of using the 8 mm diameter metal and flexible plastic cannulae for performing abortions of pregnancies of 7--10 menstrual weeks' gestation by vacuum aspiration, a comparative study was conducted. Both types of cannulae were randomly assigned to 300 subjects in a study design where the physician who performed the abortion was not the same person who evaluated the subject after the abortion or at the time of the follow-up visit. All abortions were performed under paracervical block anesthetic after mechanical dilatation of the cervix to 8.6 mm. The rates of specific complications, blood loss and the need for secondary procedures to complete the abortion were not significantly different for the two types of cannulae. The amount of tissue obtained with a routine curette check following the vacuum aspiration, and the incidence of cannula obstruction were similar for the two types of cannulae.