The individual resistances arising from current transport through the semiconductor layers and the ohmic contacts in an implant-apertured, index-guided 850 nm vertical cavity surface-emitting laser (VCSEL) have been calculated from Hall and transmission line method data. The results can be used to simulate the expected VCSEL current-voltage characteristic, which shows excellent agreement with the experimental data. This process provides a simple method for predicting the effect of changes in epitaxial layer structure thicknesses, doping, and materials on the dc characteristics of high performance VCSELs.