Addition of polyvinylpyrrolidone (PVP, molecular weight about 40,000, manufactured by General Aniline and Film Corp., Easton, Pa.) to sucrose solutions used in extraction of subcellular components improved centrifugal resolution of particulates, helped to preserve morphologic integrity of subcellular elements, and aided in preservation of enzymic activities. PVP was particularly useful in counteracting irreversible agglutination of microsomes. Best results were secured when PVP concentration was in the range 5-10% with sucrose 10-20% (pH adjusted with KOH to 8.0 -8.5 before adding tissue).