Both the alpha and the beta subunit of tubulin in Drosophila melanogaster are encoded by small multigene families. Using heterologous hybridization probes representing chicken alpha- and beta-tubulin genes, four complementary alpha- and four beta-tubulin gene sequences from Drosophila have been isolated. Each gene has been individually mapped cytogenically by in situ hybridization of nucleic acid probes to polytene chromosomes. It is clear that the genes in each family are dispersed rather than arranged in tandem arrays or clusters. Furthermore, alpha- and beta-tubulin genes are not physically linked as alpha-beta pairs. Transcripts from individual genes are differentially accumulated at particular stages of Drosophila development. This differential gene activity may provide expression of functionally specialized tubulin subunits. Alternatively, differences in expression may reflect tissue specific patterns of gene utilization.