A density sensing factor has been isolated from Dictyostelium discoideum and is known as conditioned media factor (CMF). CMF has been shown to cause starved vegetative Dictyostelium cells to differentiate into one of two cell types, stalk or spore cells. One interesting aspect of CMF concerns its release: CMF mRNA is present in vegetative Dictyostelium cells, yet secretion of the CMF protein only occurs during early and late development. My research reveals evidence that CMF is sequestered in the plasma membrane of vegetative cells. Further experiments show that CMF anti-sense transformants are motile but do not form cell aggregates. I suggest that CMF may have a role in chemotaxis which could involve interactions with components of the cytoskeleton. I have identified a few cytoskeletal components in vegetative and developing Dictyostelium cells which may provide useful information concerning the developmental process.