Measurements of total and regional cerebral blood flow in paralyzed rats maintained on 70 % N20/30 % O2obtained by a diffusible tracer technique, iodoantipyrine, and by a particle distribution method, microspheres, have been compared. Total CBF rallies were in good agreement, 0.86 ± 0.07 ml/g/mln (Paco237.3 ± 1.5, iodoantipyrine method) and 0.88 ± 0.02 (Paco, 36.2 ± 0.8, mlcrosphere method). Regional cerebral blood flows showed good agreement with the 2 methods, with highest flow in the colliculi, striatum and cerebral cortex and lowest flows in the bypothalamiis, pons medulla and cerebellum. The iodoantipyrine method is technically easier to perform and had a higher precision.