Thalidomide has shown efficacy in relapsed or refractory patients of multiple myeloma (MM). We present the adverse effect profile of thalidomide in 23 relapsed or refractory MM patients treated with this drug over a period of 15 months. Constipation (100% incidence) and sedation (87%) were the most common adverse effects. Neuropathy had low incidence and was late in onset (>12 months). Tolerance developed to sedation, constipation and skin lesions. All the adverse drug reactions were tolerable and did not warrant decrease or termination of therapy, except for peripheral neuropathy. Contrary to Western reports, peripheral neuropathy in Indian patients developed at a cumulative dose of 200 g or more after 10 months or more of therapy. Therapy was discontinued in one patient due to marked elevation of liver enzyme that was later attributed to acute hepatitis C infection. Only one patient dropped out of the trial for unknown reasons. Overall, thalidomide was found to be a relatively safe drug that can be used over a prolonged period of time.