Silver-intensified cobalt preparations reveal sex-specific neurons in the optic lobes of flies. The most pronounced of these are found in the lobula neuropil and subserve projections from the dorsal and frontal retina specifically. Two main types of male neurons have been resolved. These are single unique elements, two in each lobula, and small groups of columnar neurons. The present account describes three main features of sex-specific neurons. These are, first their shapes and dispositions; secondly, their relations with visual nerve cells that are common to both sexes, and thirdly, their exact mapping within the retinotopic mosaic of the lobula. The possible functional significance of these arrangements are discussed with respect to sex-specific visual behaviour.