A compilation of intron positions obtained from a large number of eukaryotic genomes across orthologous tubulins is explored for molecular evolution. Comparison of intron positions for 41  α, 80 β, and 30 γ tubulin genomic sequences indicates that the putative ancestral tubulin gene contained at least 19, 33, and 52 intron positions distributed at different sites in the coding regions for α, β, and γ tubulins, respectively. Many intron positions are old and are conserved across different eukaryotic lineages and intron distribution patterns are consistent with 'introns-early' hypothesis.