Studies of compressed liquid densities of butan-1-ol and of CO2 (1) + butan-1-ol (2) binary mixtures were carried out at temperatures from (313 to 363) K and pressures up to 25 MPa. Densities were measured for binary mixtures at eight different compositions (x(1) = 0.0251, 0.0857, 0.1842, 0.3749, 0.4972, 0.5965, 0.8663, and 0.9698). A vibrating tube densimeter using two reference calibration fluids was used to measure the volumetric properties. The uncertainty in the experimental densities is estimated to be better than 0.2 kg.m(-3). Densities of butan-1-ol are correlated using a short explicit volume equation and the Benedict-Webb-Rubin-Starling equation of state (BWRS EoS). Experimental densities of butan-1-ol were compared with two available correlations. The compressed liquid densities determined here for CO2 (1) + butan-1-ol (2) mixtures are the first set of data for this mixture reported in the literature. Volumes of mixing were determined using butan-1-ol densities calculated with the BWRS EoS and CO2 densities calculated with a reference EoS.