Previous ultrastructural studies of human neutrophils showed two distinctive granule types, the azurophil (peroxidase-positive) and the specific (peroxidase-negative). By identification of granules with peroxidase activity and those immunopositive for elastase antigen, the authors defined two subpopulations of azurophil granules, one that contained peroxidase activity and no measurable elastase antigen and another that contained elastase antigen associated with a small amount of peroxidase activity. They quantitated the peroxidase-positive as well as the elastase-positive granules in human peripheral blood neutrophils and found an average of 1536 +/- 69 peroxidase-positive granules per neutrophil. Of these, 399 +/- 20 were also elastase-positive. The average elastase concentration per neutrophil was 1.59 pg, and the average concentration per granule was 4 X 10(-3) pg. It is concluded that in normal individuals approximately one-third of the azurophil granules contain elastase antigen. Because neutrophil elastase has been implicated in the pathogenesis of emphysema, quantitation of its distribution within the cell presents an approach that may help define selective azurophil granule release and its relationship to the development of emphysema.