This study was designed to investigate gender differences in the USA, in anticipated professional income. Participants were 5314 medical students (3880 men, 1434 women) who entered Jefferson Medical College between 1970 and 1997. The annual peak professional income estimated at the beginning of medical school was the dependent variable and gender within selected time periods was the independent variable. Results showed significant differences between men and women on their anticipated future incomes in different time periods. Women generally expected 23% less income than men. The effect size estimates of the differences were moderately high. The gender gap in income expectations was more pronounced for those who planned to pursue surgery than their counterparts who planned to practice family medicine or pediatrics. A unique feature of this study is that its outcomes could not be confounded by active factors such as experience, working hours, age and productivity. Findings suggest that social learning may contribute to gender gap in anticipated income.