It has been recognized that metallothionein (MT) is a low molecular-weight protein and can be induced by heavy metals in several organs. Most studies on MT focus on the liver and kidney, and little is known about MT in the bone marrow. In the present study, the characterization of the MT-like protein in bone marrow of rabbits was investigated after the injection of CdCl2. A dose of 8 x 10(-5) mol/kg CdCl2 was injected subcutaneously into Japanese White Rabbits (male, 3.5 kg) for five days. Twenty-four hours after the last CdCl2 injection, the bone marrow, liver and kidney were removed immediately and frozen. The fractions of metal-binding protein were obtained by gel filtration (Sephadex G-75) of cytosol from the tissues of Cd-treated rabbit. They were heat-stable and low molecular-weight (under 10 kDa) proteins. They had high absorption at 250 nm. These observations suggest that the injection of CdCl2 induced MT-like protein in bone marrow.