Distribution of the enzyme aldehyde oxidase (AO) within the pouch of the mature wing disc is precise and differential. General locations of compartmental boundaries have been identified by fate mapping and studies of AO distribution. The suspected locations of the boundaries were verified by analyzing the distribution of AO-negative cells within an AO-stained background in gynandromorphs and in X-ray-induced clones of AO-negative cells. The anterior/posterior border appeared slightly anterior to the junction of the AO+ anterior presumptive wing surfaces and AO- posterior wing surfaces. A narrow band of AO+ cells extending proximodistally on both presumptive wing surfaces belongs to the posterior compartment. Two dorsal/ventral (dor./vent.) restrictions were found. The dor./vent. restriction equivalent to the dor./vent. border found in the adult wing was located at the ventral most edge of the AO-stained presumptive wing margin. A second restriction which was less strictly obeyed was found on the dorsal edge of the wing margin. We conclude that the whole presumptive wing margin is part of the dorsal compartment. Within the anterior wing margin an intensively stained oval was also found to be clonally restrictive. Therefore, territories were found within the prospective wing margin for which no such features have been identified in the adult Drosophila melanogaster wing.