This paper attempts to outline some of the major fatigue considerations in the design of rotary-wing vehicles. The safety and economic advantages of a “fail-safe” structure are emphasized. Fatigue considerations at both the preliminary and detail design stages are discussed. While the fatigue phenomenon is somewhat incompletely understood from an academic standpoint, it is shown how practical engineering understanding and progress have resulted from existing scientific knowledge. The importance of statistical effects is noted in regard to both manufacturer-controlled variables and operator-controlled variables. Areas of likely future progress are also pointed out.