In most Western countries where English is the medium of instruction, there is a substantial gap in student success between immigrant English as a second language (ESL) students and non-ESL students. In the United States, this situation has been observed in particular with Latino ESL students. This article describes a longitudinal study of two cohorts of Latino ESL students and compares the success of students who mainstreamed into college-level content courses and those who did not. More specifically, drawing on quantitative transcript analysis and focus group discussions, this study examines several factors impacting the mobility of Latino ESL students in a large urban community college district in the United States. The qualitative analysis focused on several themes including challenges to navigating the curriculum, the significant role of ESL in providing opportunities to use English, and the supportive role of instructors. The quantitative analysis focused on mainstreaming, enrollment patterns, and success measures, including grade point average (GPA) and course-completion ratio. The findings suggest that students who mainstream earlier or concurrently enroll in content level courses are more successful in terms of course completion and GPA. Implications of the study are discussed in relation to placement, instruction, and further areas of research. Although the ESL programs and the linguistic-minority population of this study are located in the United States, the issues raised and lessons learned can enrich the broader international conversation surrounding language minority education. (Contains 11 tables and 3 footnotes.)