The ability of B-mode ultrasound to follow effectively blood clot echogenicity changes over time under conditions of red cell preservation and lysis was evaluated. Blood clots were produced in cellulose dialysis tubing and then placed into appropriate baths of either saline or water. The echogenicity changes were then followed quantitatively using A-mode and qualitatively using B-mode imaging. Blood clots in saline showed an initial decrease followed by a leveling off in echogenicity. Blood clots in water showed a decline in echogenicity throughout the experiment. The A-mode imaging was effectively able to follow blood clot echogenicity changes under these controlled conditions.