  A path integral formula for the associative star-product of two superfields
is proposed. It is a generalization of the Kontsevich-Cattaneo-Felder's formula
for the star-product of functions of bosonic coordinates. The associativity of
the star-product imposes certain conditions on the background of our sigma
model. For generic background the action is not supersymmetric. The
supersymmetry invariance of the action constrains the background and leads to a
simple formula for the star-product.
