While investigating 2592 patients enrolled in multicenter myeloma trials, we found light chain-only (LCO) patients had worse median survival times (1.9 years) than patients with IgA and IgG paraproteins (2.3 and 2.5 years, respectively) (P < .001). However, IgA and IgG patients with levels of LC excretion similar to those of LCO patients also had poor survival times because of renal failure, resulting in worse survival during induction therapy and at relapse with no difference in progression-free survival between LCO and IgG patients. LC excretion was higher for lambda than for kappa types, but there was no difference in survival between the 2 LC types when stratified for level of LC excretion, indicating that care of renal function is vital to improving the survival of any patient with LC excretion. LCO patients were younger (P = .001), had worse performance status (P = .001), and had more lytic lesions (P < .001), perhaps reflecting late and missed diagnoses in younger and older LCO patients, respectively. No differences were observed between IgA and IgG patients in presentation characteristics, response, or survival from disease progression. The worse survival of IgA patients was attributed to shorter progression-free survival (median, 1.2 vs 1.6 years; P < .001), which is important for maintenance therapy.