The aneuploidy frequencies have been studied in vitro in lymphocytes from couples with recurrent abortions, from parents of a trisomic child and from control couples with at least two normal children; c-heterochromatin variants have been analysed on the same samples by length measurements. A significant increase of hyperploid cells has been observed in the lymphocytes from parents of a trisomic child and couples with recurrent abortions as well. However, no consistent correlation has been found so far between c-heterochromatin variants and an increase of aneuploidy.