  We define the Schur multipliers of a separable von Neumann algebra M with
Cartan masa A, generalising the classical Schur multipliers of $B(\ell^2)$. We
characterise these as the normal A-bimodule maps on M. If M contains a direct
summand isomorphic to the hyperfinite II_1 factor, then we show that the Schur
multipliers arising from the extended Haagerup tensor product $A \otimes_{eh}
A$ are strictly contained in the algebra of all Schur multipliers.
