In this paper we consider
parametric integrals with elliptic integrands depending on the surface normal. The
main result is a stability criterion for extremal immersions of those functionals,
containing a result of Barbosa and do Carmo for minimal surfaces as a special case.
Using similar techniques we are also able to show a condition for instability. The
last section contains a simple proof of the fact that the surface normal of
extremals of parametric integrals is topologically equivalent to a holomorphic
function.