The relationships between anchorage-independent growth and cytochalasin B (CB)-induced multinucleation in cloned BHK-21 cells and their chemical transformants were studied. Clones of BHK-21 cells derived from flat colonies grown on plastic, that were selected for their extremely low growth on agar plates (Ag^- clones), had low CB-multinucleated cell rates (% of cells with more than 3 nuclei), whereas parent BHK-21 cells could grow on an agar plate and had high CB-multinucleated ceil rates. Transformants (agar colonies) were induced in a Ag^- clone (L77) after treatment with MNNG and several days of expression time. At least two types of transformants were distinguishable by their agar colony morphologies; globular and dispersing. The clones derived from the transformants retained their ability to grow on an agar plate. Most showed increased CB-multinucleated cell rates when compared to parent L77 cells irrespective of the agar colony type. These results indicate that anchorage-independent growth and CB-multinucleation are closely related in BHK-21 cells and their clones, and that both properties can be induced simultaneously during chemical transformation.