We give a basic account of supersymmetric open strings and D-branes using t
he Green-Schwarz formalism, obtaining a manifestly spacetime supersymmetric
description of their spectrum. In addition we discuss a mechanism whereby
some of the D-brane states are projected out and which can lead to chiral q
uantum field theories on the brane. (C) 1999 Published by Elsevier Science
B.V. All rights reserved.