Calcium/ionomycin treatment of rabbit inflammatory exudate PMNs induces release of secondary granule contents at lower calcium doses than primary granule contents. Aliquots of EDTA-washed inflammatory exudate PMNs were incubated with increasing concentrations of calcium chloride. Suspensions were centrifuged and the supernatants analyzed as described in Materials and Methods. Release of each protein is shown at the calcium concentration at which half-maximal release occurred and is expressed as percent (mean ± SEM of 3 separate experiments) of the total content of each protein.