A method for rapid quantitative analysis of the content and distribution of short chain branching (SCB) for alpha-olefin/ethylene copolymers based on thermally fractionated DSC is presented. Eight commercial polyethylenes, four made with conventional Ziegler-Natta catalysts and four made with metallocene catalysts, were analyzed by differential scanning calorimetry (DSC), after having been thermally segregated by successive nucleation annealing (SNA). The polyethylenes were also analyzed by temperature rising elution fractionation (TREF) and carbon-13 nuclear magnetic resonance (C-13-NMR). The SNA-DSC procedure segregates polyethylenes according to methylene sequence lengths (MSL). The relationship between DSC melting temperature and SCB content was obtained by calibration with linear hydrocarbons; TREF results were not used in the SNA-DSC calibration. Deconvolution of the SNA-DSC endotherms yielded estimates of the average SCB contents and SCB distributions. The SCB contents obtained from the SNA-DSC for linear low density polyethylenes agreed very well with the SCB contents obtained by C-13-NMR and TREF, and the SCB distributions measured by SNA-DSC were very similar to those obtained by TREF. The SCB contents obtained by SNA-DSC for ultra-low density polyethylenes, made with metallocene catalysts, were about 20% lower than the values obtained by C-13-NMP, the values obtained by TREF were even lower.