This paper describes the dilemma of a system balancer when he is confronted with system effect in trying to routinely test and balance a heating, ventilating, air-conditioning (HVAC) system. Fans do not perform in accordance with their catalog ratings. They are seldom installed without restricted inlets or discharges, which creates system effect. A typical example of system effect on a fan is explored. The conclusion is that system effect must be recognized and eliminated if possible. Recommendations are given to architects, owners, engineers, fan manufacturers, sheet metal contractors, and the American Society of Heating, Refrigerating ad Air-Conditioning Engineers (ASHRAE) as to how each can help solve the dilemma caused by system effect.