Abstract: Ultrasonic pest control apparatus comprising an elongated housing having opposite ends, a sound generator carried by the housing adjacent one end thereof and including at least one transducer for providing output sound waves when driven by an electrical signal, the sound waves being directed outwardly from the end of the housing and having a frequency normally inaudible to humans and intolerable by pests such as rodents and the like, and an electrical connector element at the other end of the housing adapted to be inserted manually into a standard electrical outlet receptacle commonly found in buildings and the like. The connector can be of the prong type or of the threaded type commonly found on the base of electric lamps. The transducer preferably is driven in a manner such that the generated sound waves are a composite output in the form of a random pattern of harmonies.