Solubilities of four organic biocides in supercritical carbon dioxide were measured using a dynamic flow apparatus over a pressure range of (10 to 30) MPa and a temperature range of (35 to 80) degreesC. The biocides studied were Amical-48 (diiodomethyl p-tolyl sulfone), chlorothalonil (tetrachloroisophthalonitrile), TCMTB (2-(thiocyanomethylthio) benzothiazole), and tebuconazole (alpha-[2-(4-chlorophenyl)ethyl]-alpha- (1,1-dimethylethyl)- 1H-1,2,4-triazole-1-ethanol). Data represented the effects of temperature and pressure on biocide solubility. Measured solubilities were correlated with the density of pure solvent. The effects of methanol and acetone as cosolvents on the solubility of TCMTB and tebuconazole were determined at (50 and 65) degreesC and at selected pressures between (10 and 30) MPa. The introduction of 3 mol % acetone or methanol increased the solubilities of tebuconazole by a factor of 3 to 7. The cosolvent effect decreased with increase in pressure. At (5 to 10) mol % of cosolvent, the solubility of either biocide increased with the amount of cosolvent; however, the increase was more significant for tebuconazole than for TCMTB.