Our objective was to evaluate a gel system that uses unconcentrated urine specimens for protein electrophoresis (PEL) and immunofixation electrophoresis (IFE) in patients with monoclonal gammopathies. For the study, 222 urine specimens were analyzed by our current PEL method (Helena Laboratories, Beaumont, TX) and by a system that recommends use of unconcentrated urine (Sebia, Norcross, GA). M protein concentrations were compared in the 43 cases with a measurable M spike. IFE was performed on 111 of the samples using both methods. There was a 97% concordance for detection of PEL abnormalities. The concordance for IFE was 98%. M protein concentrations by the 2 methods correlated well (r2=0.99; slope, 1.04). Cases with insufficient urine volumes for concentration (PEL, 7; IFE, 20) were analyzed in the Sebia gel system, and in 11 cases (PEL, 2; IFE, 9) an M protein was identified.High-resolution gel electrophoresis of urine using the Sebia system offers similar performance for detection, characterization, and quantification of M proteins when compared with our current gel system. Testing unconcentrated urine specimens will mean fewer sample rejections owing to insufficient sample volume.