A high prevalence of thyroxine-binding globulin deficiency was found among Bedouin newborns in the Negev area (southern Israel) during a study lasting 2 years. This prevalence is significantly higher than those reported in other populations. Moreover, thyroxine-binding globulin deficiency was found to be more common than congenital hypothyroidism among the Bedouin. The results of thyroxine-binding globulin analysis in four patients may suggest the coexistence of at least two different mutations among the Bedouin population.