This chapter summarizes an approach to initial design and performance analysis of a high-speed hydrofoil. First, selection of the foil arrangement and foil sizing are covered, including subsidiary foils to assist take-off as used in the USSR. Determination of the drag curve is explained, as well as load sharing between fore and aft foils, interference effects, appendage, and strut drag. Dynamic stability of hydrofoil craft is covered next, including control of foil immersion. Maneuverability and directional control with rudders and elevators are summarized. Seakeeping performance is discussed including normal operation with the hull clear of waves and the consequences of interaction with the hull. Sample motion and acceleration data are presented. Automated flight control systems are introduced in some detail.