The optimization of conditions and media for the in vitro culture of molluscan cells have yielded advances such that primary cultures can now be maintained for weeks or months. With one exception, molluscan cells have proven refractory to the establishment of continous cell lines. Knowledge derived from these studies has helped investigators maintain and grow intramolluscan parasites in vitro.Recent advances in cell fusion, cell cloning and transfection of oncogenes have yet to be applied in molluscan cell culture. Once established, future cell lines will permit a great variety of studies including the control of gene expression, post-transcriptional processing including glycosylation, and the production in quantity of molluscan factors such as lectins, hormoned, immunogenic macromolecules and others of interest. In addition these lines will also facilitate screening for molluscan viruses and other cellular pathogens, and the propagation of these putative agents of biological control. Such cell lines would also permit the study of molecular mechanisms of drug and hormone actions, and the rational design of drugs.Molecular genetic protocols have been restricted so far to studies of evolution and systematics within molluscan taxa. Both RNA and DNA probes are being developed from ribosomal, mitochondrial and nuclear compartments. Both direct sequencing and restriction length polymorphisms detected using endonucleases are yielding useful data.