The efficacy of stem cell transplantation in amyloidosis largely is determined by treatment-related mortality rates (range, 11-25%). Appropriate patient selection is essential to avoid this high mortality rate. Among 271 patients undergoing stem cell transplantation, troponin T was a powerful predictor of treatment-related mortality. Patients with troponin T levels of 0.06 microg/L or higher had a day-100 all-cause mortality rate of 28%. Patients with troponin T levels less than 0.06 microg/L had a day-100 all-cause mortality rate of 7% (P < 0.001). Troponin T levels should be measured in all patients before transplantation. Those with troponin T levels exceeding 0.06 microg/L should be considered for less toxic therapies until the clinically optimal use of stem cell transplantation is better defined by randomized clinical trials.