ABSTRACTEysenck's (1967) hypotheses concerning Extraversion, Neuroticism, and physiological reactivity were tested in relation to habituation. A factorial design, varying Extraversion (three levels) and Neuroticism (two levels) was employed: 60 subjects, 10 per cell. Both tonic and response measures of electrodermal activity (skin conductance) were recorded.The results showed: (1) High Neurotics were more reactive than Low Neurotics (for two measures of habituation and total number of responses); (2) Extraversion was inversely related to spontaneous activity; (3) Latency of first response was moderately related (10% level only) both to Neuroticism (inversely) and to Extra‐version (directly); (4) Tonic conductance measures failed to discriminate between groups; (5) Measures which discriminated between personality groups were inter‐correlated.Since the measures taken were related to both Extraversion and Neuroticism, the findings do not support Eysenck's prediction that these measures are related to Extraversion al