Cells from four species of Lepidoptera larvae known to be susceptible to several intracellular pathogens were cultured in vitro. Undifferentiated cells had the greatest potential for growth and survival. Imaginal wing disc explants formed extensive monolayers as a result of cell migration and mitosis. Mitoses were abundant in prohemocytes but not in other types of hemocytes. Differentiated larval tissues were unsuitable sources of cells for continuous culture. Migration of cells from these tissue explants was limited, and those cells which isolated themselves from the explant did not divide.