The feasibility and utility of calculating efficiency curves for HPGe detectors using the MCNP 4B transport code are explored. The calculated curves are compared to experimental data obtained from a 137Cs source counted on a HPGe detector. Efficiency data for the four centimeter reference location are reported in this work. The detector, shield, and counting fixtures are included in the model. This work also involved extensive sensitivity analyses. Sensitivity studies focused on seven parameters involving the active area of the germanium crystal. Three of the seven variables were found to be significant.