Several variables influencing the recovery of Factor VIII in the cold-precipitated protein fraction were examined. The actual rate at which the physical-chemical conversion of plasma from a solid to a liquid state occurs does not seem to affect the yield. Rather, it is the amount of time immediately postthaw and prior to centrifugation that determines the Factor VIII activity in the cryoprecipitate. With prolonged periods at 4 C the Factor VIII activity leaves the cold precipitate and lifts into the supernatant. Even distribution of the plasma layer and close attention to the thawing procedure facilitate Factor VIII recovery.