Two women previously treated with cyclophosphamide had five pregnancies, resulting in seven normal offspring, including two sets of twins. All the babies had normal chromosome constitution and there was no significant chromosome damage. Apart from the twin pregnancies, which were induced, the pregnancies continued to full term and the birth weights were good. Men with renal transplants receiving azathioprine and prednisolone fathered 13 pregnancies, resulting in 11 offspring; one was a mongol; there were two spontaneous abortions, including a twin pregnancy. With the exception of the mongol, the babies had normal chromosome constitution and there was no significant chromosome damage. Two women with renal transplants receiving azathioprine and prednisolone have had four pregnancies, two ended in spontaneous abortion and two continue.