The solubility of nonanoic acid (also known as pelargonic acid) in supercritical carbon dioxide has been determined at (313.15 and 333.15) K over a pressure range of (10 to 30) MPa. The experimental apparatus was of a flow-type, dynamic design, and the solubility was obtained gravimetrically. The solubility ranged from a pelargonic acid concentration of (0.14 +/- 0.07) kg.m(-3) (333.15 K, 10.0 MPa) to (25.39 +/- 0.61) kg.m(-3) (313.15 K, 30.0 MPa). The results showed that the solubility of pelargonic acid at 313.15 K was always greater than at 333.15 K at each pressure considered, a common behavior in liquid + SCF phase equilibria. No supercritical. fluid solubility data for pelargonic acid were found in the literature. To ensure the validity of the experimental technique, solubility data for oleic acid were measured and compared to literature values. Oleic acid solubilities agreed with literature data within estimated uncertainties. A modified Adachi-Lu model, in terms of dimensionless variables, was used to correlate the solubility of pelargonic acid. Excellent agreement between experimental data and the correlation was found.