A model is described which leads to an analysis of data on the sequence of sexes in human families, particular attention being given to the detection of a correlation between the sexes of adjacent sibs. Three sources of potential confounding with this correlation are discussed. The method of analysis avoids any confounding with the effects of voluntary limitation of family size, or with the effects of variation in the probability of a male from birth to birth within a family. It is more difficult to separate the effect of correlation between the sexes of adjacent sibs from the effect of variation between families in the probability that a child born to the family will be male. The problem was solved in the present investigation by using an auxiliary analysis to show that families did not, in fact, differ in this probability. If this were not so, a separation of the two factors could still have been made by an additional analysis referred to in the paper.