  A recent paper by Moore and Witten explained that Ramond-Ramond fields in
Type II superstring theory have a global meaning in K-theory. In this note we
amplify and generalize some points raised in that paper. In particular, we
express the coupling of the Ramond-Ramond fields to D-branes in a K-theoretic
framework and show that the anomaly in this coupling exactly cancels the
anomaly from the fermions on the brane, both in Type IIA and Type IIB.
