In the present study, we evaluated in mouse and rat mast cells if adriamycin uptake is related to histamine release. In addition, the uptake of the antineoplastic drug and histamine release were studied in other normal and neoplastic cell lines. The effect of sodium cromoglycate was also examined. Adriamycin induced histamine release from mixed or purified mast cells of the mouse and rat. This exocytotic response was quantitatively related to intracellular concentrations of adriamycin. Significant differences in adriamycin uptake were observed between mast cells and other normal and neoplastic cells. When peritoneal mast cells were treated with sodium cromoglycate, histamine release and adriamycin uptake were significantly reduced. In contrast, incubation of other cells with cromoglycate only slightly reduced the cellular concentration of the antineoplastic drug.