Patients with early-stage myeloma are typically observed without therapy until symptomatic disease occurs. However, they are at high risk of progression to symptomatic myeloma, with a median time to progression of approximately 1-2 years. We report the final results of a phase II trial of thalidomide as initial therapy for early-stage multiple myeloma in an attempt to delay progression to symptomatic disease. In total, 31 patients with smoldering or indolent multiple myeloma were studied at the Mayo Clinic. Two patients were deemed ineligible because they were found to have received prior therapy for myeloma, and were excluded from analyses except for toxicity. Thalidomide was initiated at a starting dose of 200 mg/day. Patients were followed-up monthly for the first 6 months and every 3 months thereafter. Of the 29 eligible patients, 10 (34%) had a partial response to therapy with at least 50% or greater reduction in serum and urine monoclonal (M) protein. When minor responses (25-49% decrease in M protein) were included, the response rate was 66%. Three patients had progressive disease while on therapy. Kaplan-Meier estimates of progression-free survival are 80% at 1 year and 63% at 2 years. Major grade 3-4 toxicities included two patients with somnolence and one patient each with neuropathy, deep-vein thrombosis, hearing loss, weakness, sinus bradycardia, and edema. Thalidomide has significant activity in early-stage myeloma and has the potential to delay progression to symptomatic disease. This approach must be further tested in randomized trials.