We describe how to assay plasma total CO2 automatically, discretely, and highly specifically by infrared absorption spectrometry. Plasma, 50 mul, is sampled in disposable capillaries and inserted into a block wherein the specimens are protected from exposure to air. A sequencer advances the block and signals a dispenser to flush the sample into a reaction vessel with 2.6 ml fo 50 mmol/liter H2SO4. After 24 s of incubation, the evolved CO2 is swept into a 1-meter infrared gas cell by a stream of nitrogen. A recorder displays the resulting peak in absorbance units. Operation of all valves controlling gas and liquid flow is regulated by the sequencer. In the present version, the time required for analysis of one sample is 65 s. The sample size may be reduced by at least 10-fold and the time sequence accelerated to assay 70-80 specimens per hour.