This study compared gradient gel electrophoresis (GGE) and light-scattering (LS) methods of determining low density lipoprotein (LDL) particle size. LDL was isolated from 27 fasting subjects. Peak particle size was determined by GGE on 3-13% gradient gels (Gradipore, Sydney, Australia) and by LS using a Zetasizer 3000 (Malvern Instruments, Malvern, UK). Repeated measurements on a single specimen indicated a coefficient of variation (CV) of 0.3%. A correlation was noted (P < 0.0001; r = 0.78) when comparing LDL particle size determined by LS methodology and GGE. Particle diameter results obtained by LS were smaller than those obtained by GGE (23.1 +/- 0.1 vs. 26.1 +/- 0.1 nm; P < 0.0001). LDL particle size determined by LS methodology correlated inversely with the log of triglyceride level (P < 0.0001; r = -0.77) and positively with high density lipoprotein (HDL) cholesterol level (P < 0.002; r = 0.57).