  Schramm-Loewner Evolutions ($\SLE$) are random curves in planar simply
connected domains; the massless (Euclidean) free field in such a domain is a
random distribution. Both have conformal invariance properties in law. In the
present article, some relations between the two objects are studied. We
establish identities of partition functions between different versions of
$\SLE$ and the free field with appropriate boundary conditions; this involves
$\zeta$-regularization and the Polyakov-Alvarez conformal anomaly formula. We
proceed with a construction of couplings of $\SLE$ with the free field, showing
that, in a precise sense, chordal $\SLE$ is the solution of a stochastic
"differential" equation driven by the free field. Existence, uniqueness in law,
and pathwise uniqueness for these SDEs are proved for general $\kappa>0$.
