Polyribosomes were obtained in high yield from Rhynchosciara salivary glands by a method which uses the non-ionic detergent Nonidet P 40, in moderate salt buffer and DTT as RNase inhibitor. The polysomal profiles from glands of animals which have just started to spin the communal cocoon are slightly but consistently different from those obtained from about 5 day older animals, in which DNA puffs were open in the salivary gland chromosomes. The heaviest polyribosomes which could be detected by either radioactive uridine or amino acid incorporation have 8 to 9 ribosomes. The data indicate the existence of stable messengers in the salivary glands. © 1975.