Let M be a closed connected
3-manifold such that π2(M) = 0. Suppose that π1(M) is a nontrivial free product
with amalgamation across the group of a closed connected surface S other than the
projective plane or 2-sphere. Then it is shown that there is an embedded surface S in
M “realizing” the group structure above.
Our theorem also considers the case when M has boundary and gives an answer
to a problem of Neuwirth.