A modified technique for continuous recording of the Hb-O2 association curve for blood samples is proposed. The following alterations to the classical method of Duvelleroy et al. (5) were studied and validated: 1) dilution of blood micro-samples (200-400 mul) to 10 ml of a buffered phosphate solution; 2) use of a (CO2, O2) mixture allowing the maintenance of standard conditions (pH=7.40, PCO2=40 Torr) during the entire oxygenation process. The advantages of such modifications were: 1) reducing the time necessary for both deoxygenation and drawing Hb-O2 association curve (to about 20 min), hence permitting to work out large series of samples; 2) avoiding the necessity of imprecise a posteriori corrections, thus permitting analysis of the different components of the BOHR effect.