A 42-year-old man presented with a six-month history of a slowly-enlarging ulcer on his right sole, a 30-year history of altered pigmentation of the trunk and extremities, and hyperkeratotic papules of the palms and soles. Histopathologic examination showed an invasive squamous-cell carcinoma of the right sole and hyperkeratosis with keratinocyte atypia of the left finger and left lateral foot. The clinical and histopathologic findings are consistent with chronic arsenicism, which most commonly occurs in the setting of drinking contaminated water or after occupational exposure. Evaluation should include a physical examination, basic laboratory work-up, and measurement of a 24-hour urine arsenic concentration. Vigilant surveillance for the development of cutaneous malignancies is required. Oral retinoids may be helpful in reducing hyperkeratosis secondary to chronic arsenicism.