AbstractAs a part of a research project on the mass transfer in liquid pulsed sieve‐tray extraction columns (PSE), the diameters and hold‐ups of the drops were measured: the drop size using a suction technique, with photoelectric detection, which was adapted to the special boundary conditions of the PSE; the integral hold‐up by the pressure difference between the lower and upper parts of the column. Since experimental results cannot be described by known calculation formulae for the Sauter mean diameter and the hold‐up, a new method of calculation was developed. It is phenomenologically based on high‐speed photographs of the drop motion on a sieve tray. The mathematical‐physical model allows the prediction of drop size and hold‐up within certain limits, while the possible different operating regimes of the PSE, i.e. the mixer‐settler and dispersion regimes can al