Tertiary amine local anesthetics, such as dibucaine and tetracaine, have been found to reversibly modify the blood-borne implantation and experimental metastatic properties of B16 melanoma cells in syngeneic C57BL/6 mice. Local anesthetic treatment in vitro of low (B16-F1) and high (B16-F10) lung-colonizing melanoma variants reduced significantly their abilities to form lung tumor colonies, but the cells recovered their original in vivo colonizing properties within several hours after drug removal. Low drug concentrations (0.5 mM tetracaine) that altered the metastatic properties of these cells did not modify cell plating efficiencies or tumor growth rates at subcutaneous sites. With the use of [125]-5-iodo-2'-deoxyuridine-labeled B16 cells, the kinetic distributions of viable tumor cells in mice were also shown to be altered. Fewer cells were initially localized and retained in the lungs, and more cells reached extrapulmonary sites. Local anesthetics modified B16 cell morphology, inducing cell rounding and loss of microvilli. These effects occurred concomitant with alterations in microfilament organization. Anesthetic-treated cells also exhibited decreased cell-adhesion characteristics in both homotypic and heterotypic (endothelial and subendothelial matrix) cell-adhesion assays. Despite these changes, cell surface lactoperoxidase-catalyzed iodination of external proteins and labeling of cellular glycoproteins on polyacrylamide gels with 125I-labeled lectins did not reveal differences in the displays or quantities of cell surface glycoproteins after drug treatment. The data are consistent with the idea that reversible disruptions in transmembrane cytoskeletal control induced by local anesthetics result in alterations in cell shape, loss of stable adhesive interactions, and a decrease in blood-borne arrest and metastatic properties.