To test the hypothesis that the magnitude of sex differences in simple visual reaction time (RT) has narrowed across time, a meta-analysis was conducted on 72 effect sizes derived from 21 studies (n = 15, 003) published over a 73-year period. The analysis provided strong evidence for the hypothesized change. In addition, the analysis indicated that the sex difference in RT was on average smaller with non-U.S. samples than with U.S. samples. No relation was found between the magnitude of the sex difference in RT and age or presence vs. absence of a warning signal. Two factors-participation in fast-action sports and driving-are proposed as having been responsible for the decrease in the magnitude of the sex differences in simple visual RT across time.Perusal of the records for timed sports events reveals two progressions over the course of the past century. One is that the winning times decreased for both men and women. The other is the rate of decrease was greater for women than men. Illustrative of these trends are the winning times for the 100-m run in the Olympic Games (World Almanac and Book of Facts, 2003). For women, this event was introduced into the Olympics in 1928; therefore, I will use this year as the base year to compare the two sexes. In that year, the winning time was 10.8 s for men and 12.2 s for women, a difference of 1.4 s. In 2000, the winning time for men was 9.84 and 10.75 s for women, a difference of .91 s. Thus, over this 72-year period, the winning times decreased by 8.9% for men and 18.9% for women, and the difference between the two sexes decreased by 64.5%. Of further note is that the winning time for women in 1928 was only .2 s slower than the winning time for men in 1896 and that the winning time for women in