BACKGROUND/AIMS Inconsistent evidence is available that different ethnic groups exhibit differences in skin physiological parameters. Recently, variations in hair follicle morphology have been described, although the influence of such variations on the follicular penetration process has not been investigated until now. METHODS The aim of the present study was thus to investigate skin physiological parameters, follicle morphology and the penetration process in different ethnic groups. RESULTS AND CONCLUSION Whereas no significant differences with regard to skin physiological parameters could be observed, morphological analysis of the hair follicles revealed, inter alia, that Caucasians had significantly larger terminal hair follicles than Asians and Africans. The surface of the hair follicle infundibulum was shown to be 3% in Caucasians, 2.6% in Africans and 2.4% in Asians. The investigations into penetration revealed no significant differences after a 30-min penetration time, whereas after 24 h, the Asian volunteers presented significantly larger amounts of sodium fluorescein in the hair follicles and the stratum corneum, which may be explained by cultural habits.