Reference values for peripheral red and white blood cells, platelets and coagulation parameters from 11 and 18-week-old Charles River Sprague Dawley rats [Cr1:COBS CD(SD)] were obtained using automated methods. The Coulter Model S Senior, the Clay Adams Ultra-Flo Platelet Counter and the Sherwood Lancer Coagulyzer, were used to measure these parameters on 25 rats/sex. Detailed information on instrumentation or assay methods, and the animals, their source, environment and blood collection method was given. Platelet counts were in the range of 694 X 10(9)/1 to 1412 X 10(9)/1 which was higher than previously reported. In general, the remaining ranges were similar to previously published reference ranges.