The clinical course and histologic findings of cutaneous adverse reactions associated with bortezomib treatment are presented in this study. Bortezomib (Velcade) is a proteasome inhibitor, which is used as a novel anticancer drug in the treatment of multiple myeloma. We have conducted an observational analysis of 47 patients with myeloma who were treated with bortezomib in 3 prospective clinical trials. Cutaneous adverse reactions were observed in 6 patients (13%). Five patients presented with sharply demarcated erythematous plaques or nodules on the trunk and one patient had generalized morbilliform erythema with ulcerations and fever. The time between the first bortezomib dose and occurrence of the cutaneous eruptions was at least 30 days. The cutaneous eruptions usually resolve within a few days. One patient withdrew from further treatment because of severe cutaneous toxicity. The histologic findings ranged from perivascular dermatitis to interstitial and interface dermatitis corresponding with clinically more extensive lesions.