Circadian rhythmicity in the average proliferation rate of the primary spermatogonial cell crop in the frog testis was studied by the stathmokinetic method. Colchicine was used to specifically block cells after they enter metaphase. Thein vivomitotic activity of primary spermatogonia was studied in three different periods of the year and was analyzed at 8 time points of the 24‐hour day. Circadian variations were suggested in all three periods of the year. Mitotic activity of the primary spermatogonia was also analyzedin vitroat 16 time points through a 48‐hour experimental period. Daily rhythmic fluctuations in the division rate of primary spermatogonia were observed. Thus, the proportion of cells in mitosis within the primary spermatogonial cell crop of the frog testis exhibits not only significant seasonal variations (as reported elsewhere), but also a daily rhythmic variation. The percent difference between low and high values of mitotic circadian rhythm varies with season.