A new method that allows rapid phenotyping of genetic Lp(a) glycoprotein types in large numbers of samples is described. The method is based on sodium dodecyl sulfate gel electrophoresis of reduced serum or plasma in horizontal slab gels followed by immunoblotting with polyclonal anti-Lp(a) lipoprotein or monoclonal anti-Lp(a) glycoprotein antibodies. Phenotyping of 194 unrelated, healthy subjects resulted in Lp(a) allele frequencies of Lp(a)B = 0.013, Lp(a)S1 = 0.032, Lp(a)S2 = 0.106, Lp(a)S3 = 0.096, Lp(a)S4 = 0.156, and Lp(a)O = 0.600, and confirmed the recently recognized association of Lp(a) glycoprotein phenotype with Lp(a) lipoprotein concentration. The new procedure is suitable for large-scale population, genetic, and epidemiologic studies and may be important for atherosclerotic risk assessment.