Granulocytes have been isolated by counterflow centrifugation-elutriation (CCE) from canine leukocyte-rich blood obtained by continuous-flow centrifugation leukapheresis (CFCL). We have attempted to define both the maximal granulocyte recovery and the efficiency of granulocyte purification for the Beckman JE6 elutriation rotor when large volumes of leukocyte rich blood are utilized. The efficiency of granulocyte purification by CCE is 81% (1.31 +/- 0.1 x 10(9) PMNL) if the number of granulocytes entered into the Beckman JE-6 rotor as leukocyte rich blood is limited to 1.60 +/- 0.13 x 10(9) PMNL. Approximately 96 +/- 2% of the leukocytes in the purified fraction were of the granulocytic series with mononuclear leukocytes comprising the residual 4% of the cell population. In vitro analysis of the isolated granulocytes indicated that the cells did not lose their morphological integrity or physiological function as a result of the dual CFCL/CCE procedure relative to granulocytes isolated by CCE from freshly drawn peripheral blood.