The injection system for the Frascati Phi -factory was designed to store approximately=10/sup 13/ positrons and electrons in the two main rings. The system will consist of a high-current electron linac, a low-current high-energy electron-positron section, and a compact damping ring. The two linac sections will provide approximately=0.3nC of positrons within +or-1% energy spread in 10-ns pulses for injection at 50 Hz into a single 76-MHz bucket of the damping ring. Extraction of the high-quality damped bunch from the accumulator will take place at 1 Hz, filling one main ring bucket at a time. The linac design foresees 3-m-long 2 pi /3TW constant gradient accelerating sections with SLED systems to increase the energy gain. The magnetic structure of the damping ring was designed to be accommodated in a 12-m*12-m hall, and is made of four quasi-achromatic bending sections and four long straights to accommodate injection and extraction pulsed elements and the RF system.<<ETX>>