Despite the increase in data and the understanding of both deterministic effects and cancer induction in the skin in recent years, many questions that are important for risk estimation remain. This report, adopted by the ICRP in November 1991, is the work of a Task Group set up to consider the biological basis for dose limitation in the skin. The Task Group reviewed available dose-effect data for cancer induction and deterministic effects in the skin to estimate for these effects; it reviewed evidence concerning which cells are at risk, to determine at what depth dose measurements should be made, and re-examined dosimetry considerations and weighting factors for skin, with reference to the effects of `hot particles' and ultraviolet radiation. The information collated in this report was used by the Commission to set dose limits and the weighting factor for skin in the 1990 Recommendations of the ICRP.