The contribution of flow distribution to shell-side mass transfer performance in randomly packed hollow fiber modules is determined using a random fiber distribution model and the Leveque equation without fitting parameters. Comparisons were made between theoretical results and measurement of oxygen stripping in actual hollow fiber modules in counter-current flow. Modules of packing densities ranging from 8.4 to 70.2% were used. The observed mass transfer coefficients decreased rapidly with increasing packing density until 50% volume fraction was reached and increased again at higher packing densities. The theoretical results showed the same trend but significantly underestimated the mass transfer at low packing densities. The influence of entry and transverse flow increased overall mass transfer at low packing densities over that predicted purely by laminar axial flow. Preliminary work with laser speckle flow visualization of the module shell confirmed these observations. Comparisons with existing literature correlations are discussed, and strategies to assess the level of flow redistribution and flow variation are presented.