Modules containing from 120 to 27,000 parallel hollow fibers 100 μm in diameter can separate mixtures by reversed phase chromatography. The mixtures separated include aqueous solutions of ketones using alkanes as the stationary phase, and aqueous solutions of the proteins myglobin and cytochrome‐c using an octane solution of reversed micelles as the stationary phase. The dispersion observed in these separations is comparable to that predicted from the Aris‐Taylor theories. Modules of these fibers promise a lower pressure drop and a greater reproducibility than columns of spheres of equivalent surface area per volume. Such modules can facilitate scale‐up of liquid chromatography.