Pesticides include chemicals as well as biological and physical agents used to control a diverse array of pests. Although a number of occupational and non-occupational situations affect the extent and route of exposure to pesticides, most skin effects are associated with a relatively small number of compounds. The highest exposures and risk of dermatitis involve individuals employed in agricultural pest control operations. The degree of pesticide contact may be lessened by use of protective clothing and engineering controls such as closed mixing and loading systems. For evaluating the effects of pesticides on the skin, the most relevant tests include dermal absorption tests, the 72 hr. Draize dermal irritation study, and sensitization studies. For the Draize irritancy test, a general protocol utilizing albino rabbits is provided. Suggested concentrations are also given for sensitization studies using the patch test methodology. Registries for monitoring pesticide-related illness exist in numerous US and worldwide jurisdictions. The most complete historical data derive from the California Pesticide Illness Surveillance Program. This chapter briefly presents data on illnesses associated with individual classes of pesticides and pesticide mixtures, discussed separately as five categories (antimicrobials, fumigants, fungicides, herbicides, and insecticides), focusing on the principal causes of pesticide dermatitis reported in medical literature and in California use and surveillance data between 1982 and 2014.