Using Michigan Panel Study of Income Dynamics (PSID) data, the authors study the slowdown in the convergence of female and male wages in the 1990s compared to the 1980s. They find that changes in human capital did not contribute to the slowdown, since women's relative human capital improved comparably in the two decades. Occupational upgrading and deunionization had a larger positive effect on women's relative wages in the 1980s than in the 1990s, explaining part of the slower 1990s convergence. However, the largest factor was a much faster reduction of the "unexplained" gender wage gap in the 1980s than in the 1990s. The evidence suggests that changes in labor force selectivity, changes in gender differences in unmeasured characteristics and in labor market discrimination, and changes in the favorableness of demand shifts each may have contributed to the slowing convergence of the unexplained gender pay gap.