The influence of the container walls on the pressure drop of packed beds is investigated. A detailed analysis of more than 2300 experimental data points reveals the Reynolds number dependence of this effect. Physical evidence is given that the observed behavior is caused by the counteracting effects of the wall friction and the increased porosity near external boundaries. A comparison of the predictions of 24 published pressure drop correlations with available experimental data shows that Reichelt's approach (Chem. Ing. Tech. 44 (1972) 1068) of correcting the Ergun equation for the wall effect is the most promising one. Improved correlations are obtained for different types of packings by fitting the coefficients of that equation to the database.