Time-lapse films of micromass cultures prepared from stage 19-24 chick embryo wing buds indicate that the majority of the mesenchymal cells present undergo little net movement, even during the formation of prechondrogenic aggregates. Rather, these cells undergo mitosis and pulsatile movements in place. In the same cultures, round or elongate myoblasts could be observed migrating as single cells on or between the mesenchymal cells. These in vitro observations are consistent with the suggestion that migratory myoblasts may establish the myogenic pattern in the limb by extensive migration through the nonmigrating limb mesenchyme.