Fractional precipitation based on the difference in solubility of crude paclitaxel dissolved in methanol, to which distilled water must be added, is the most effective method for the pre-purification of paclitaxel. In this study, the effect of the distilled water feeding and mixing method on the efficiency of fractional precipitation and the formation of paclitaxel precipitate were evaluated. When the distilled water was added all at once, the highest purity (similar to 57.0%) and yield (similar to 81.0%) were obtained, and a spherical precipitate was formed by the clustering of crystal branches. On the other hand, when the distilled water was added intermittently in several aliquots, the purity and yield tended to decrease with increasing number of additions, and the precipitate took the form of a cross or pentagon with less clustering of branches. Not mixing after the addition of distilled water resulted in high purity (similar to 57.0%) and the formation of a spherical precipitate that showed increased branching around the nucleus over time. In contrast, when the sample was mixed intermittently after adding distilled water, paclitaxel was obtained in high yield (similar to 99.7%). Continuously mixing the sample after adding distilled water, however, caused the precipitate crystals to be broken into smaller pieces. (C) 2010 Elsevier Ltd. All rights reserved.