45 women out of a total of 58 patients who followed a dietary regime appropriate to the sex they had chosen for their babies were successful in delivering a baby of the wanted sex. This result gives a success figure of 77.6% (the mean between 67 and 89%: p less than 0.001) and from the statistical point of view this difference is significant as compared with the natural sex ratio. The diets were overall well tolerated and the children at birth weighed normal weights. The parents seemed to request approximately equal numbers of girls as of boys--a balanced request. A high number of patients abandoned the method (75%). This is explained by the restrictions that are imposed by the diets and because the method would still appear to be experimental. It does seem that the ability to influence the sex ratio of the future offspring is possible when the ionic balance of the diet is changed. The study should be continued.