Part I - Test Procedure: methods and instrumentation for testing mechanical draft and natural draft cooling towers. Part II - Evaluation of results: method for evaluation of the performance of mechanical draft cooling towers using both characteristic curves and performance curves; natural draft and natural draft-fan assisted cooling towers using characteristic curves and performance curves. The results are expressed in terms of water cooling capacity. Part III - Appendix: example evaluation of mechanical draft cooling tower, natural draft cooling tower, and fan-assist cooling tower using either characteristic curve method or performance curve method; calculation of KaV/L; enthalpy tables; facsimiles of ATC-106 Test Forms. Revised September 2022