  We discuss metric perturbations produced during a period of inflation in the
early universe where two scalar fields evolve. The final scalar perturbation
spectrum can be calculated in terms of the perturbed expansion along
neighbouring trajectories in field-space. In the usual single field case this
is fixed by the values of the fields at horizon-crossing, but in the presence
of more than one field there is no longer a unique slow-roll trajectory. The
presence of entropy as well as adiabatic fluctuations means that the
super-horizon-sized metric perturbation $\zeta$ may no longer be conserved and
the evolution must be integrated along the whole of the subsequent trajectory.
In general there is an inequality between the ratio of tensor to scalar
perturbations and the tilt of the gravitational wave spectrum, which becomes an
equality when only adiabatic perturbations are possible and $\zeta$ is
conserved.
