Forty-eight subjects were assigned to four equal-size cells defined by sex and familial handedness (presence versus absence of an immediate family member who is left-handed or ambidextrous). Subjects were presented a series of 40 stimuli, each of which was designed to represent the intersection of a sensory mode (visual versus auditory) and hemisphere mode (verbal versus spatial). The dependent measures were the number of stimulus-specific and nonspecific responses with magnitude larger on the lefthand. On the whole, results are supportive of the contralateral inhibitory process hypothesized by LaCroix and Comper (1979). Nonspecific response data appear to be sensitive to hemispheric manipulation as observed previously in this laboratory. Sensory mode appears to be an important determinant of lateralized phasic magnitude differences, with males showing the most striking verbal-spatial distinctions during visual mode presentation.