Amsacrine induces cytoplasmic rods in cultured epithelial cells derived from adult rat liver hepatocytes (ARL6T). Rods become visible two hours after treatment of cells with 10 microM amsacrine. At 24 h, multiple rods are present in nearly every cell. Ultrastructural examination of treated cells reveals structures 5-10 microns in length and 0.2 to 0.3 micron in width. These rods are not found in untreated ARL6T cells. This consistently-induced morphologic finding represents a newly described drug effect. The mechanism of formation of these rods and their role in amsacrine cytotoxicity is at present unknown.