The duration of the mitotic cycle and its phases was measured in the root tips of two crops (1966 and 1974) ofTriticum durumcv. Cappelli, by autoradiographyc technique, after labelling with3H-thymidine. The average total duration of the mitotic cycle was found to be 18h 45′ in crop 1966 and 16h 25′ in crop 1974. This time included, in crop 1966, a synthetic period (S) of 9h 35′, a post-synthetic period (G2) of 2h 36′, a mitotic duration of about lh and a pre-synthetic period (G1) of 5h 36′. In crop 1974, S was found to be 9h 20′, G24h 30′, mitosis 56′ and G1lh 38′. The single phases duration was also considered as percentage of the total time of the cycle.