The v + gene of Drosophila and its associated enzyme, tryptophan pyrrolase, were employed in a study of the relationship between dosage compensation and the location of the gene in the genome. Enzyme assays performed on various genotypes indicate that although differently positioned genes may specify different enzyme activities, they still show dosage compensation. In each rearrangement examined, the enzyme activity associated with the gene is at least twice as much in males as it is in females. The relevance of this and earlier data with respect to models for regulation is discussed.