OBJECTIVE: The purpose of the current study was to test the specificity of an association between eye tracking abnormality and schizophrenia spectrum personality symptoms in the family members of schizophrenic patients. The studies of biological markers for genetic vulnerability to schizophrenia, which test an association between a biological measure and schizophrenia spectrum personality symptoms, are constrained, since these personality symptoms may lack the specificity for a schizophrenic phenotype. An association between a behavioral measure and these personality symptoms in general can easily be false (i.e., not related to schizophrenic vulnerability). In contrast, a strong deviant finding in the relatives of schizophrenic patients with spectrum personality symptoms, in the presence of a relatively normal finding in spectrum subjects without a known history of schizophrenia, makes the biobehavioral measure an interesting candidate for such investigations. METHOD: Seventy-five subjects recruited from the community who did not have a family history of psychosis completed the study (24 of the 75 had significant schizophrenia spectrum personality symptoms). Thirty-two first-degree relatives of schizophrenic patients (13 with spectrum symptoms) completed the study. Subjects were 18-45 years old and had no DSM-III-R axis I diagnosis. RESULTS: Qualitative smooth pursuit eye movement score was significantly worse in relatives with the spectrum symptoms than in spectrum subjects without a family history of schizophrenia and the nonspectrum relatives. Schizotypal and schizoid symptoms explained a significant amount of the variance in the eye tracking measure in the relatives (31% and 20%, respectively) but not in the community subjects (less than 2%). Relatives of schizophrenic patients with and without the spectrum symptoms had significantly longer antisaccade latency, in spite of comparable latency for visually guided saccades, than the community subjects. CONCLUSIONS: Smooth pursuit abnormality in subjects with schizophrenia spectrum personality disorders is specifically associated with a family history of schizophrenia.