Maximum likelihood mixed stock analysis was used to identify the natal origin of immature loggerhead turtles (Caretta caretta) in a tropical developmental habitat in Caribbean Panamá. Approximately 65-70% of the loggerhead turtles in Chiriquí Lagoon originate from South Florida nesting beaches, and the other 30-35% originate from Mexico. Haplotype frequencies of the Chiriquí Lagoon loggerhead population are significantly different from those observed in the pelagic environment in the eastern Atlantic, and estimated nesting beach contributions to Chiriquí Lagoon are significantly different from values expected if recruitment were based solely on the size of nesting populations. These observations suggest that dispersal of loggerheads into benthic developmental habitats from the pelagic environment is not random. The occurrence of US and Mexican loggerheads in tropical developmental habitats has not been previously recognized. Exploitation and other mortality factors operating in the Caribbean area must be taken into account in demographic models and management plans for these two populations. This exploitation could be particularly important for the small, demographically vulnerable Mexican population and for other small populations for which no genetic data are currently available.