Background: Roifman syndrome (OMIM 300258) is a multi-system disorder with a physical phenotype that includes B-cell immunodeficiency, intra-uterine and postnatal growth retardation, spondyloepiphyseal dysplasia, retinal dystrophy and characteristic facial dysmorphism. So far, six cases, all boys, have been reported in the literature. Roifman postulated that the syndrome may be due to a mutation in an X-linked gene or an autosomal gene giving rise to a sex-limited trait, but the definitive pathogenetic mechanism has still not been elucidated. Very little is known about the cognitive and behavioural phenotype of Roifman syndrome and no standardized measures of cognitive abilities have been reported. Methods: We report the seventh case of a boy with Roifman syndrome and present the first systematic documentation of the cognitive and behavioural phenotype of an individual with the syndrome. Results: In spite of having been reported as appearing intellectually "able," formal evaluation showed very significant intellectual disability and neuropsychological impairment across cognitive domains. Conclusions: The findings suggest that Roifman syndrome may be an example of an X-linked mental retardation syndrome (XLMRS).