This study addresses two fundamental questions about the economic assimilation of undocumented immigrants in the United States: 1) how different recently legalized immigrants are from all foreign-born persons and native-born whites; 2) whether wages of undocumented immigrants improve as they acquire greater amounts of U.S. experience and, if so, how these improvements are comparable to those of immigrants in general. We analyze the Legalized Population Survey and the Current Population Survey to assess the returns to U.S. experience and find positive returns to U.S. experience for both undocumented migrants and all foreign-born men. Returns to U.S. experience depend on region of origin. Undocumented immigrants from Mexico received the lowest wage returns and men from non-Spanish-speaking countries received the highest returns to U.S. experience.