BACKGROUND: Previous analyses have found variable results when evaluating the size of the association between intellectual ability and adaptive functioning in individuals with impaired function. METHODS: We assessed the association between intellectual ability measured as a latent higher-order g and three different areas of adaptive functioning in a sample of clinically referred individuals with low IQ. RESULTS: Regressing g on conceptual, practical and social adaptive functioning yielded standardised regression coefficients of 0.65, 0.60 and 0.51 respectively. CONCLUSIONS: Results suggests that even at low levels of ability, increments in g still have important consequences for human functioning. Further, the influence of g may not be equally strong across different areas of human functioning.