Studies have reported that certain measures of intrafamilial transactions are associated with an increased risk both for the initial onset of schizophrenia and for its recurrence following the initial episode of disorder. Two of the most studied of these are communication deviance (CD), a measure of subclinical thought disorder expressed in speech, and expressed emotion (EE), defined as notable attitudes of criticism and/or emotional overinvolvement manifested in a semistructured interview. A previous study (Goldstein et al. 1992) examined whether these two measures were associated with the presence of a diagnosable psychiatric disorder in the biological parents of recent-onset schizophrenia patients. In general, they were not. The present study went one step further. It examined whether these same measures were correlated with family history of schizophrenia or affective disorder in the biological parents and siblings of these same parents. High EE was not associated with a greater family history of schizophrenia spectrum disorders among the parent's parents and siblings but was unexpectedly found to be inversely associated with familial affective disorders. In contrast, CD was associated with a family history of schizophrenia spectrum disorders among the parent's parents and siblings. The findings are consistent with the possibility that CD may be an indicator of a genetic vulnerability factor for schizophrenia.