1. 1. Lymphocytes to be used for tissue typing procedures can be stored at room temperature in a nutrient medium for periods of up to 3 wk without an intervening change of fluid medium. 2. 2. Fresh or nutrient medium stored lymphocytes can be frozen in bulk quantities until they are required for tissue typing studies, and/or 3. 3. Depending upon the facilities of the laboratory (1) fresh, (2) nutrient medium stored, and (3) frozen and thawed cells can be distributed into 72-well tissue typing trays, frozen for either short or long term studies under controlled rate procedures and stored in the vapor phase of liquid nitrogen for future typing studies.