In a total sample of 105 triploid spontaneous abortions and live-born and stillborn infants, the parental origin could be determined in 77%. Dispermy was the most common cause of this abnormality. Among the digynic triploids 69% resulted from retention of the second polar body. Parental ages did not differ from those of the general population except for 10 aneuploid triploids with significantly elevated parental ages. In five sibships, simple aneuploidy in another pregnancy was observed, four of them being potentially viable. Two sisters had triploid conceptions. There were four twin pregnancies, a frequency of one in 26. Only two triploids had an XYY sex chromosome complement, one of which was mosaic with loss of an autosome and the other was a chimera. A frequency of almost 50% of mothers exposed to preconception abdominal radiation is suggestive of an association between radiation and triploidy and requires further investigation.