This study investigated the effect of precipitation time and temperature on the efficiency of fractional precipitation during the purification of paclitaxel. The kinetics and thermodynamics of this process were also analyzed. Fractional precipitation was carried out at different temperatures (-10, 4, 7, 8, 10 degrees C) and the highest yield was obtained in the shortest time at 4 degrees C. The Johnson-Mehl-Avrami-Komolgorov (JMAK) equation was applied to the experimental data and nucleation and growth were found to take place simultaneously at precipitation temperatures of -10, 4, 7, and 8 degrees C, while these processes occurred in a consecutive manner at 10 degrees C. In addition, the transformation rate (rate constant k = 1.810 x 10(-5) min(-1)) was the highest at 4 degrees C, suggesting that this temperature is ideal for fractional precipitation. Analysis of thermodynamic parameters also confirmed that fractional precipitation was exothermic, irreversible, and spontaneous at 4 degrees C.