Of 70 process schizophrenic patients clinically assessed and tested for reaction time, 40 showed reaction time crossover. Of the 40 with crossover, 53 of their first degree relatives were clinically assessed and tested. Five of the relatives, found to have psychotic symptoms, were analyzed separately. Also, 41 control subjects without personal or family history of psychiatric disturbance were clinically assessed and tested. The nondisturbed relatives had reaction time crossover (regular minus irregular) significantly greater than the (expected) negative values of the normal control subjects, but not significantly greater than a zero value within subjects. When disturbed and nondisturbed relatives were combined, greater differences indicative of crossover occurred. On the other hand, the relatives, as expected, did not show the slow mean reaction time characteristic of diagnosed schizophrenic patients.