By means of a lexical decision task in which words and nonwords were controlled for familiarity, the question whether sex and familial handedness influence right-field superiority for righthanded subjects was investigated. Analyses of unimanual reaction times and response accuracy revealed sex differences and a cognitive-motor interference for the male group. For hit rates the men, reacting with their right hands, showed a right-field superiority for words and a left-field superiority for meaningless syllables, and the men reacting with their left hands showed the reversed asymmetry. Theoretical problems associated with reaction time and hit rate asymmetry as indicators of language lateralisation are discussed.