Recent reports using cross-sectional data indicate an increase in the percentage of wives who outearn their husbands, yet we know little about the persistence of wives' income advantage. The present analyses utilize the 1990-1994 waves of the National Longitudinal Survey of Youth 1979 (N = 3,481) to examine wives' long-term earnings advantage. Although a significant minority of women outearn their husbands in 1 year, considerably fewer do so for 5 consecutive years. The presence and persistence of wives' income advantage vary by demographic characteristics, economic and human capital measures, and over the individual and marital life course. The findings suggest caution in interpreting women's relative economic gains as signaling absolute progress toward eliminating gender inequality within marriages.