The unsteady aerodynamics of a single-stage high-pressure turbine has been the subject of a study involving detailed measurements and computations. Data and predictions for this experiment have been presented previously, but the current study compares predictions obtained using the nonlinear harmonic simulation method to results obtained using a time-marching simulation with phase-lag boundary conditions. The experimental configuration consisted of a single-stage high-pressure turbine (HPT) and the adjacent, downstream, low-pressure turbine nozzle row (LPV) with an aerodynamic design that is typical to that of a commercial high-pressure ratio HPT and LPV. The flow path geometry was equivalent to engine hardware and operated at the proper design-corrected conditions to match cruise conditions. The high-pressure vane and blade were uncooled for these comparisons. All three blade rows are instrumented with flush-mounted, high-frequency response pressure transducers on the airfoil surfaces and the inner and outer flow path surfaces, which include the rotating blade platform and the stationary shroud above the rotating blade. Predictions of the time-dependent flow field for the turbine flow path were obtained using a three-dimensional, Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) code. Using a two blade row computational model of the turbine flow path, the unsteady surface pressure for the high-pressure vane and rotor was calculated using both unsteady methods. The two sets of predictions are then compared to the measurements looking at both time-averaged and time-accurate results, which show good correlation between the two methods and the measurements. This paper concentrates on the similarities and differences between the two unsteady methods, and how the predictions compare with the measurements since the faster harmonic solution could allow turbomachinery designers to incorporate unsteady calculations in the design process without sacrificing accuracy when compared to the phase-lag method.