The solubility of disodium salt hemiheptahydrate of ceftriaxone in different concentrations of acetone in water at T = (298.15,308.15, and 318.15) K was measured by using gravimetrical method. The density of the saturated solution was also determined with the help of a digital densimeter (Anton Paar, model DMA 45) at corresponding temperatures. The solubility of disodium salt hemiheptahydrate of ceftriaxone increases with increasing temperature, but decreases with increasing concentration of acetone in the solution. The experimental data were correlated with equation (4). The correlation is satisfactory with the average absolute deviation of 1.67 g (.) kg(-1) mixed solvents. (C) 2004 Elsevier Ltd. All rights reserved.