It has been claimed that mothers with certain hormonal imbalances and/or immunological disorders are more likely to give birth to male than female children and that they are more likely to give birth to a neurodevelopmentally disordered (ND) child. Liederman and Flannery (1995) reported that the sex ratio of families with an index ND child did not significantly differ from the sex ratio of families without an index ND child. The data were derived from the National Collaborative Perinatal Project (NCPP). James (in the current issue) challenged us to reconsider the standard against which we judged the sex ratio of siblings of ND children, since the 1.10 sex ratio that we obtained for the siblings of non-ND children is much higher than the sex ratio of children born during that period according to the U.S. Census Bureau. In the current paper, the NCPP data were re-examined and it was demonstrated that the high sex ratio of siblings in our non-ND sample was not due to various retention or recruitment biases. Thus, we suggest that use of the sex ratio of siblings of non-ND children was the proper standard against which to judge the sex ratio of ND families, and that our data provide no evidence to support the notion that these families are male biased.