Client drop out from treatment is of great concern to the substance abuse field. Completion rates across modalities vary from low to moderate, not ideal since length of stay has been positively and consistently associated with better client outcomes. The study explored whether client characteristics shown to be related to retention were associated with treatment completion and treatment duration for a sample of 164 Latino substance users who entered a culturally focused residential program. In-person client interviews were conducted within a week of program admission. Logistic regression analysis was used to examine research questions. Clients most likely to drop out had self-reported co-occurring psychiatric diagnoses; they were 81% less likely to complete the program, suggesting that clients with mental health problems have a more difficult time remaining in residential treatment. Clients using drugs in the three months prior to entry were three and a half times more likely to be in the shorter stay group, and clients who lived in institutions prior to program entry were three times more likely to be in the longer-stay group. Factors contributing to drop out for this Latino sample were similar to those identified in the literature for non-Latino samples. Methods for addressing the needs of clients with co-occurring disorders are discussed. (Contains 3 tables.)