The problems involved in the design and the construction of a wideband transistor amplifier for use in a submerged repeater are discussed in the paper. The maximum transmission frequency is 4284 kc/s.The amplifier consists of two three-stage feedback amplifier units. Only one type of transistor is used throughout to simplify reliability assessment. The factors leading to the choice of this type from among those commercially available are discussed. A brief account of the special components employed, and their effect on the design of the amplifier, is given.Several prototype models and the amplifiers used in the repeaters have been constructed to the design given in the paper. Two repeaters have been installed in the St. Margaret's Bay-La Panne No. 6 cable to extend the circuit capacity from 216 to 420 channels.