Loss of serotonergic and dopaminergic neurons may have serious implications for normal brain function. Drosophila models of neurodegenerative diseases utilize the short life-span and simple anatomy of the fly to characterize the molecular and genetic processes characteristic of each dysfunctional state. In fly embryonic and larval ventral nerve cords, serotonergic and dopaminergic neurons are positioned in a stereotypic pattern that is reorganized during metamorphosis. In this study, we examine the adult pattern of serotonergic and dopaminergic neurons within the adult fly ventral nerve cord. We find that the number of cells lost following metamorphosis is highly variable. Changes in cell number attributable to age are therefore likely to be highly masked by developmental variation. The source of this variation is probably apoptosis-based cell loss during pupal development.