A unique laboratory system for evaluation of agricultural tractor engines and power trains has been developed which closely simulates field loading, operates on a continuous 24 h basis, and is fully automated to reduce manpower expense. The programming hardware in conjunction with a dynamometer system provides a continuous and efficient method of indoor evaluation which correlates well with results from field test units. A master load histogram produced from collected field data was used to derive an engine loading cycle. A data logging system monitors the test stands during unattended times. Certain shortcomings-lack of reaction to environmental conditions, geographical differences, an operator's “feel” of a vehicle-will not totally eliminate field testing.