This paper is concerned with the production of PhDs in the United States and Canada in the post-WW II period, overall and by gender and major discipline. The effects of the explanatory variables lagged six years are consistent with the model. Military conscription with educational exemptions and the Vietnam War increased male PhD production in the U.S., but have no effect for U.S. females or in Canada. Government expenditures on research and development enhanced PhD production, especially for males and in the physical sciences in the U.S. A higher rate of growth of non-farm productivity encouraged PhD production in the U.S., but not in Canada. The cyclical indicator, the adult male unemployment rate, has a weak positive effect for males in both the U.S. and Canada, suggesting that the negative effect of the opportunity cost of time was stronger than the positive wealth effect. Other variables the same, there has been an increase over time in PhD production for females, but there is no such trend for males. The result has been an increase over time in PhD production for both males and females, but the faster increase for females has narrowed the gender gap.