Cloud point extraction has been used for preconcentration of trace amount of copper. The analyte was complexed with 1,2-dihydroxyanthraquinone-3-sulfonic acid sodium salt, and octylphenoxypolyethoxyethanol was added as a surfactant. The effects of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction were studied. Under the optimum conditions, preconcentration of a 12 mL sample solution permitted the detection of 1.07 ng mL(-1) of copper with an enrichment factor of 21. The method was applied to the determination of trace copper in water samples.