The noise of an axial fan can be significantly reduced by carefully designing the blade shape for the local fan environment. Reduction in both the broadband spectrum of fan noise and of fan tones by >8 dBA are achievable, with no loss in fan efficiency. This paper presents some of the acoustic and aerodynamic design factors that must be correctly accounted for in the fan design. Results are shown for three successful low noise fan designs, where careful attention was paid to three-dimensional flow effects. Some of the pitfalls of low noise fan design are outlined.