AbstractThis study chronicles leukocyte‐ and erythrocyte‐depleted platelet concentrate collection by a dual. stage channel in which three variables: 1) donor peripheral blood platelet concentration, 2) total blood processed, and 3) collection volume were statistically correlated with platelet yield as determined by a multiple regression analysis of single variables. Platelet concentration in the final yield was related to donor precount and collection rate, and could be varied as indicated for individual applications. Total blood processed was established by procedure time, which in turn was defined by citrate‐induced calcium changes in the donor. Reduction in peripheral blood platelet concentration averaged 24% for a mean platelet yield of 3.8 × 10′. An average of 40% of transfused platelet concentrates were recovered in recipient peripheral blood 1 hr posttransfusion and were hemostatically effective, as determined by correction of bleeding time. Platelet yields and patient response were sustained during current collection procedures, verifying the principles described during the investigativ