Disturbances in language functioning may be associated with familial vulnerability to schizophrenia. Language comprehension, measured by the Luria-Nebraska Relational Concepts Factor Scale, was evaluated in 36 schizophrenic probands and their nonschizophrenic adult brothers (n = 41), and in 18 normal controls. Language comprehension performance was a function of psychiatric diagnosis in the brothers. Brothers who met criteria for schizophrenia-spectrum disorders showed significantly reduced language performance compared with unaffected brothers and normal controls. Moreover, abnormal language performance was exhibited by significantly more probands and spectrum-disordered brothers than by the normal controls and the brothers without schizophrenia-spectrum disorders. Finally, language performance was not significantly different for 31 pairs of schizophrenic probands and their brothers. Impaired language comprehension appeared comparatively specific in this sample of relatives, as groups were not significantly different on measures of nonlinguistic concept formation (Wisconsin Card Sorting Test) and general intellectual functioning (WAIS-R Information and Block design). Results suggest that impaired language comprehension is associated with familial vulnerability to schizophrenia, and that this disturbance may be most severe in relatives diagnosed with schizophrenia-spectrum disorders.