As a basis for other experiments using flow cytometry of porcine peripheral blood leukocytes, cell fractions were isolated by various methods and analyzed by forward angle light scatter and 90 degree light scatter. Cytospin smears of cell samples were also studied by leukocyte differential counts and nonspecific esterase staining. Three main populations of peripheral blood leukocytes [lymphocytes, monocytes, and granulocytes (primarily neutrophils)], were defined in the log 90 degree light scatter by forward angle light scatter histogram. Partial overlap was observed between lymphocyte and monocyte, and between monocyte and granulocyte domains. Correlation between leukocyte differential counts and flow cytometric quantification based on bitmap statistics of appropriate domains was between r = 0.872-0.892 for lymphocyte and granulocyte. Percoll density gradients were used for subfractionation of leukocyte populations, especially for the enrichment of granulocytes. The specific densities were calculated for lymphocytes (1.0585-1.0819 g/cc), monocytes (1.0585-1.0702 g/cc), granulocyte (1.0819-1.0936 g/cc), and erythrocytes (greater than 1.0952 g/cc). We suggest that light scatter characterization is a basis for future studies of porcine blood by flow cytometry.