  Anomalies in Yang-Mills type gauge theories of gravity are reviewed.
Particular attention is paid to the relation between the Dirac spin, the axial
current j_5 and the non-covariant gauge spin C. Using diagrammatic techniques,
we show that only generalizations of the U(1)- Pontrjagin four--form F^ F= dC
arise in the chiral anomaly, even when coupled to gravity. Implications for
Ashtekar's canonical approach to quantum gravity are discussed.
