The aim of the research presented here was to determine whether low concentrations (1 μg/ml) of a highly specific microtubule depolymerizing agent, nocodazole (NOC), affects the meiosis ac tivation process in conjugating pairs of the ciliated protozoanBlepharisma japonicum. In order to identify and quantify differen ces in meiosis, both NOC treated and untreated coeval pairs were stained and examined for their meiotic phases. A clear‐cut delay in the progression of meiosis in treated pairs was found. The findings indicate that NOC reversibly inhibits meiosis induction and that treated pairs need both continuous cell union and a period of recovery in order to progress through meiosis after NOC is with drawn. These results suggest that cytoplasmic microtubule dynamics may be involved in the meiotic activation processs ofBlepharismaconjugating pairs.