In a series of 74 women with systemic lupus erythematosus (SLE) there were 43 who became pregnant during the period of study. The 43 women had 111 pregnancies, all together, of which 81 occurred before and 30 after the onset of SLE. Of the 111 pregnancies, 20 ended in presumably spontaneous abortions, of which 11 occurred before and 9 after the onset of SLE. In the 81 pregnancies that occurred before the onset of SLE, the incidence of presumably spontaneous abortions was 14%; in the 30 that occurred after the onset, the incidence was 30%. Detailed records of the course of SLE before and after pregnancy were available in 12 cases; the 12 patients had 29 pregnancies. In 6 of the 12, symptoms of SLE were first observed during pregnancy or soon post partum. There was no evidence that pregnancy mitigated the course of SLE.