The hemolytic characteristics of 14 different polydimethyl-siloxane materials were studied, using a rotating disk device to shear whole human blood for 6000 sec. Disk surfaces included commercial Silastic products with and without silica filler, coatings formed from hexa-methyl and tetra-methyl disiloxane monomer vapors by glow discharge, and heparinized silicones. Results are presented in the form of kinetic hemolysis curves (KHC)--plots of plasma hemoglobin vs. time--and analyzed in terms of the slopes of these curves in the 1500-6000 sec region where the KHC is nearly linear. It was found that most silicone products are low-hemolysis materials, comparable to polyethylene (PE) but often about 20% less ehmolytic; one product was superior by about 40%. The only consistent exceptions to this were the glow discharge surfaces from HEXA-methyl disiloxane (15-80% poorer than PE) and heparinized surfaces (70-280% more hemolytic than PE).