We present a theorem that determines the value of the Wilson loop associate
d with a Nambu-Goto action which generalizes the action of the AdS(5) x S-5
model. In particular, we derive sufficient conditions for confining behavi
our. We then apply this theorem to Various string models. We go beyond the
classical string picture by incorporating quadratic quantum fluctuations. W
e show that the bosonic determinant of D-p-branes with 16 supersymmetries y
ields a Luscher term. We confirm that the free energy associated with a BPS
configuration of a single quark is free from divergences. We show that unl
ike for a string in flat spacetime in the case of AdS(5) x S-5 the fermioni
c determinant does not cancel the bosonic one. For a set-up that correspond
s to a confining gauge theory the correction to the potential is attractive
. We determine the form of the Wilson loop for actions that include non-tri
vial B-mu nu field. The issue of an exact determination of the value of the
string Wilson loop is discussed.