Growth of highly invasive B16 melanoma BL6 cells with bromodeoxyuridine (BUdR) decreases in vitro cell detachment and modulates extrapulmonary growth in vivo. We now show: (1) The presence of an 80 kd glycoprotein in the Triton-insoluble matrix of control BL6 cells but not in the corresponding fractions from BUdR-treated BL6 cells and poorly metastatic F1r cells. (2) The matrix fractions from the two last mentioned cells reveal Triton-insoluble glycoproteins of about 55-58 kd. (3) Mild trypsin treatment of intact cells before matrix preparation leads to the preferential disappearance of the 80 kd component from control BL6 matrix, suggesting its extracellular localization. (4) Prevention of Triton-mediated BL6 matrix detachment by zinc chloride pretreatment, and analysis of different BL6 clones with significant metastatic behavior, also revealed the presence of 80-90 kd matrix-associated glycoproteins in control but not in corresponding BUdR-grown cultures. Since BUdR decreases cell detachment, extrapulmonary metastasis and the levels of the 80-90 kd Triton-insoluble glycoprotein species in metastatic B16 melanoma, and this matrix component is also decreased in poorly metastatic F1r cells, we propose an involvement of this glycoconjugate in tumor cell detachment and metastatic behavior.