During the National Oceanic and Atmospheric Administration's Ocean Atmosphere Carbon Exchange Study expedition in the eastern North Atlantic in summer 1993, measurements of four CO2 parameters, along with hydrographic properties, were made: fugacity of CO2, fCO2 (measured at 20 ¿C and in situ); pH (measured at 20 ¿C); total inorganic carbon, TCO2; and total alkalinity, TA. The major objective of this cruise was to establish a benchmark against which future measurements of the transient invasion of CO2 can be made. The large-scale distributions of surface water CO2 parameters were related to temperature and salinity in this region. The subsurface TA and TCO2 measurements were fitted to multiple linear functions of salinity, in situ temperature, apparent oxygen utilization, and silicate. The measurements of the inorganic carbon system were also used to examine the internal consistency of the carbonate system in this area. The measurements were internally consistent to ¿1.3% in fCO2, ¿0.006 in pH, ¿3 μmol kg-1 in TCO2, and ¿3 μmol kg-1 in TA if proper carbonic acid dissociation constants are used for different input combinations. The thermodynamic constants of Goyet and Poisson <1989>, Roy et al. <1993>, Millero <1995>, and Lee and Millero <1995> were most consistent with the measurements of pH (at 20 ¿C), TCO2, and TA. However, if fCO2 (at 20 ¿C) is used in thermodynamic calculations, the constants of Mehrbach et al.<1973> gave the best representation of measurements. The constants of Lee and Millero <1995> were also reasonable agreement with these measurements.¿ 1997 American Geophysical Union