Under the hypothesis of analyticity of the data with respect to the tangent
ial variable we prove the existence and uniqueness of the mild solution of
Prandtl boundary layer equation. This can be considered an improvement of t
he results of [8] as we do not require analyticity with respect to the norm
al variable. (C) 2001 Academie des sciences/Editions scientifiques et medic
ales Elsevier SAS.