Structural and functional properties of high-density lipoprotein (HDL) after short-term freezing in the presence or absence of 10% sucrose were compared with HDL stored at 4 degrees C. Freezing did not affect the size of HDL particles or their antiinflammatory and antioxidant properties. Freezing slightly impaired the ability of HDL to support cholesterol efflux from human macrophages, but this property was preserved when HDL was frozen in the presence of sucrose. Freezing also resulted in approximately 10% loss of HDL in the samples. We conclude that freezing HDL in the presence of 10% sucrose preserves its structural and functional properties.