We provide a test of the thesis that Protestantism influenced the development of modern capitalism by using quantitative data from 1500 through 1870. Results show that during this period the percentage of a country's population that is Protestant is unrelated to both its level of per capita GDP and the average rate of its annual growth in per capita GDP. We conclude that the thesis that the Protestant ethic has been an important factor in the growth of modern capitalism is not supported. (Contains 1 figure, 2 tables, and 1 note.)