The solubility of (S)-Boc-piperazine ((S)-3-[[(1,1-dimethylethyl)amino] carbonyl]-1-piperazinecarboxylic acid 1,1-dimethylethyl ester) and the racemic compound of (S)- and (R)-Boc-piperazines in supercritical carbon dioxide was measured in the pressure range from (9 to 20) MPa and at temperatures (308.2, 318.2, and 328.2) K using a flow-type apparatus. The experimental solubilities of (S)-Boc-piperazine and the racemic compound at the present conditions were in the range of (2 x 10(-4) to 7 x 10(-3) and 4 x 10(-5) to 6 x 10(-4)) in mole fraction, respectively. The solubilities were correlated by the Soave-Redlich-Kwong (SRK) equation of state with two binary interaction parameters. The present model gave a good correlation of all the experimental solubility data. The two binary interaction parameters were correlated by linear functions of temperature.