Flow patterns and mixing properties of micromixing devices described in Pall I are investigated by computational fluid dynamics (CFD) and semianalytical methods. The CFD results provide qualitative information on mixing, but, due to numerical artifacts, no quantitative information can be derived in most cases. The geometrical arrangement of liquid lamellae predicted by the CFD simulations explain transmitted-light experiments reported in Part L In contrast, the semianalytical method provides a simple model for the mixing devices presented and allows to assess their mixing properties. For two Of the four micromixers, mixing times were in the range of milliseconds, thus lending themselves to fast, mass-transfer-limited reactions. Experimental data obtained for a specific micromixer support the semianalytical model. Both the model and experiments suggest that geometric focusing of a large number of liquid streams is a powerful micromixing principle.