The Booster for the National Synchrotron light Source electron storage rings is a 100–700 MeV synchrotron with 28.35 meter circumference. Its design current is 20 mA and its repetition rate is 1 Hertz. The lattice consists of four superperiods, each containing two focusing quadrupole magnets and two defocusing bending magnets. Nominal tunes are υX=2.42, υy=1.37. Small values of βx and ηx in the bending magnets allow a damped emittance ∊x=5.6xl-8 meter radians. Details of the lattice, beam dynamics and beam injection and ejection are presented. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.