Flagellar excision in Chlamydomonas reinhardii triggers a rapid and extensive induction of tubulin synthesis. Cloned plasmids, pFT beta 1 and pFT beta 2, carrying cDNA inserts complementary to beta-tubulin mRNA, have been prepared and used to demonstrate a direct requirement for tubulin mRNA synthesis during tubulin induction. Increased tubulin mRNA synthesis is detected within 5 min after deflagellation. During the 45 min peak period of tubulin synthesis, tubulin mRNA accumulates to levels 15- to 35-fold higher than those found in control (non-deflagellated) cells. In addition, there appears to be a direct correlation between tubulin mRNA concentrations and the levels of tubulin production during the induction and deinduction cycle that accompanies flagellar regeneration. Amiprophosmethyl (APM), a compound we reported earlier as a selective inhibitor of tubulin synthesis in deflagellated cells, is shown to block the accumulation of tubulin mRNA following flagellar excision and to cause the rapid loss of tubulin mRNA from cells treated at the peak of induction.