New data are reported on chemical and mechanical factors affecting the hemolysis of blood in a rotating-parallel-disk apparatus used in biomaterials studies described elsewhere. The hemolytic potential for a blood is found to correlate with plasma components LDH and total triglycerides existing prior to shear. Antibiotics are shown to suppress hemolysis, unrelated to bacterial action. The kinetics of measured hemoglobin release are analyzed in terms of a red cell population having a distribution of fragilities, sample storage age, and possible hemoglobin adsorption. Blood/gas interfacial effects are examined by varying the gas and the extent of interface, and found to be minimal under normal testing conditions. Several geometric and dynamic parameters are varied to illustrate the complexities of engineering design and scale-up.