Dermal exposure gains in significance by the same token as permissible occupational inhalation exposures are lowered. The contribution of dermal absorption to the total dose absorbed during occupational exposure is apparent when dermal and pulmonary uptake rates are compared. Development of an experimental data base for evaluation and control of dermal exposure is hindered by: lack of suitable methods for measurement of dermal absorption in humans; interspecies differences in skin permeability; regional differences in absorption rates due to non-homogeneity of skin composition and perfusion rates over the body; possible skin damage induced by the chemical or dispersant; and exposure conditions in the workplace. In the absence of sufficient human data, theoretical models can provide satisfactory information on dermal absorption. It is advocated that the current practice of using acute dermal toxicity (LD50) as a criterion for warning on the potential of significant dermal absorption be replaced by a criterion based on comparison of the dermal penetration rate with the pulmonary uptake rate at inhalation exposures permissible in the workplace.