The effectiveness of dextran (CSC-6%), OPG (Baxter-5%), and MFG (Knox-3%), as colloidal infusion fluids, was compared with blood and saline (0.9%) in 53 dogs subjected to 2 hemorrhagic shock procedures: (1) controlled bleeding to a blood pressure of 20 mm. Hg followed by immediate infusion of a volume equivalent to the bleeding volume, and (2) 1 hour of hypotension (30-35 mm.Hg) prior to infusion. In both procedures repeated controlled bleedings to 20 and 30 mm.Hg, respectively, were performed at 3 and 24 hrs. postinfusion. The ratio of a subsequent bleeding to the initial, termed the bleeding volume index (BVI), blood pressure, hematocrit, and survival were recorded over a 24-hr, period. No significant differences were detected among the 3 colloidal solutions in the treatment of the acute hemorrhage of Proc. I. BVI values at 3 hrs. were: blood -97, dextran - 87, MFG-83, OPG -78, and saline-54. All treated dogs survived Proc. I. In the hypotensive shock procedures MFG appeared somewhat more effective than OPG or dextran. The BVI values at 3 hrs. postinfusion were : blood-72, MFG-67, dextran-53, OPG-34, and saline -12.-W. M. Parkins.