Background：Arsenics have been used for various medical purposes. These arsenics can cause different kinds of cutaneous and internal malignancies. The arsenic-induced malignancies can be fatal or cause severe morbidity. Objective：For early detection and prevention of the arsenic-induced malignancies, the authors analyzed the clinical characteristics of arsenic-induced skin diseases. Methods：Medical records of 15 patients(10 males, 5 females) with arsenical keratosis(AK) during a period from September 1994 to October 1999 were reviewed. Interview, physical examinations, skin biopsy, and laboratory tests were performed. Results：14 patients used Korean proprietary pills(KPP, "Hwan-Yak"), which were suspected to contain certain amount of arsenics, as a drug for treatment of certain diseases such as vitiligo(4 patients, 26.7%), laceration, syphilis, etc. The other formulation of medication was Salvarsan injection. Age at KPP or Salvarasan medication was from seven to thirty-five years old. Duration of medication was from one month to four years. Bowen's disease(BD), squamous cell carcinoma(SCC) and basal cell carcinoma(BCC) were detected in ten(66.7%), three(20%) and one(6.7%) patients, respectively. One(6.7%) patient had lung cancer. Sites of predilection were palmoplantar area(100%) for AK, trunk(60%) for BD and lower extremities(45%) for SCC and BCC. Conclusion：Chronic exposure to arsenic can induce the cutaneous and systemic malignancies. To prevent these malignancies, strict managements and supervising programs on certain arsenic-containing drugs(probably KPPs) are required, and regular cutaneous and systemic examinations for the patients with AK should be performed. (Korean J Dermatol 2000;38(11)：1461~1467)