This presentation focuses on the four most important skin diseases in Taiwan thought to be of environmental and/or occupational origin. The majority of work-related dermatoses are contact dermatitis patients. Among occupational contact dermatitis patients, 58.5% involved irritant and 41.5%, allergic dermatitis. Electronics, hairdressing, medical practice, and construction were the most important occupations causing contact dermatitis. An endemic occurrence of chronic arsenism causing hyperpigmentation, keratosis, and cancer has been reported in Taiwan. Arsenical skin cancers present as multiple lesions at different disease stages. The skin cancers are usually found in non-sun-exposed areas. UVB exerts an inhibitory effect on the proliferation of arsenical cancers; this may explain its non-sun-exposed nature. An outbreak of premalignant and malignant skin lesions was reported among paraquat manufacturers in 1985. The skin lesions were mainly distributed over the sun-exposed areas. Photodamage and photocarcinogenesis revealed a strong association with exposure to bipyridines among paraquat manufacturers. In 1979, a mass poisoning occurred in Taiwan from cooking oil contaminated by polychlorinated biphenyls (PCBs). Over 60% of patients were in grades O-II by the Japanese classification. The blood PCB levels of the Taiwanese patients were found to be higher than those of the Yusho subjects.