  We show an equivariant bordism principle for constructing metrics of positive
scalar curvature that are invariant under a given group action. Furthermore, we
develop a new codimension-2 surgery technique which removes singular strata
from fixed point free $S^1$-manifolds while preserving equivariant positive
scalar curvature. These results are applied to derive the following
generalization of a result of Gromov and Lawson: Each closed fixed point free
$S^1$-manifold of dimension at least 6 whose isotropy groups have odd order and
whose union of maximal orbits is simply connected and not spin carries an
$S^1$-invariant metric of positive scalar curvature.
