Explants isolated from Jerusalem Artichoke tubers are stimulated to divide when placed in contact with a nutrient medium containing sucrose, mineral salts, coconut milk, and 2: 4-dichlorophenoxyacetic acid. The first two or three cell divisions, which only occur in the outer layers of the explant, do not occur uniformly with time but are, at least, partially synchronous. This synchrony, which decreases with successive divisions, is inherent. DNA synthesis, which is an essential prerequisite for division in these cells, is also partially synchronous. These conclusions, while being of some significance in relation to the interpretation of the early development of the callus, are also of some interest in relation to the possible exploitation of this system for the study of cell division.