The O2 affinity and the Pco2-pH dependence were studied in blood samples from 20 healthy subjects at temperatures of 28 and 32 °C. The O2 dissociation curves were determined at various CO2 pressures (Pco2 = 30, 40 and 50 mmHg); the Pco2-pH dependence was determined at various So2 degrees. Comparison of the determined O2 dissociation curves with results obtained at temperatures of 37 and 40 °C [Grote] yielded the following relationship at constant Pco2:Δ log Po2=0.0242 ΔT. The log Pco2/pH lines, determined for various So2 degrees, converge when Pco2 increases. The results of both series of tests can be summarized in alignment nomograms for the respiratory gas values and pH values. These show clearly the interdependence of the o2 and Co2 dissociation curves of blood at temperatures of 28 and 32°C. The nomograms can serve as supplementary means of judging the respiratory gas transport in the blood and the gas exchange during hypothermia. Provided two of the five parameters Po2, So2, Pco2, Cco2 and pH are known, the remaining three can be derived from the nomograms. Limitation: blood must be normal with respect to [Hb] and [BB].