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Abstract: In suspended culture, most relevant for biotechnological application, plant cells form aggregates. This phenomenon is of importance as it is related to productivity, leads to local heterogeneities, and might be a reason for the considerable shear sensitivity of these cultures. The valid measurement of plant cell aggregates, however, is not trivial, due to a rather large size distribution and measurement artifacts implied by the measuring method. In this study, laser diffraction was used as a novel method for characterization of Taxus chinensis cells, a major source for the antitumor agent paclitaxel. Aggregate size measured in shaking flask cultivations over 10 days revealed an increase during the growth phase of a batch cycle and a decrease during the stationary phase. During growth, the increase in bio dry weight was proportional to aggregate size. Laser diffraction was found superior to microscopy and image analysis, which had a tendency to underestimate aggregate size up to 20%. This novel approach provides a practicable, rapid, robust, and reproducible way to analyze a 100-fold more samples in considerably less time than image analysis and is therefore of especial value for quality control in industrial plant cell cultivation.