  A promising approach for obtaining improved approximation algorithms for
Steiner tree is to use the bidirected cut relaxation (BCR). The integrality gap
of this relaxation is at least $36/31$, and it has long been conjectured that
its true value is very close to this lower bound. However, the best upper bound
for general graphs was an almost trivial $2$. We improve this bound to $3/2$ by
a combinatorial algorithm based on the primal-dual schema.
