The disposition of cadmium was examined in the earthworm Eisenia fetida using two exposure media, filter paper, and artificial soil. Uptake and elimination rates were estimated to be 0.03039 and 0.00895 hr-1, respectively, for 1.25 micrograms Cd/cm2 filter paper exposure and 0.00512 and 0.00029 hr-1, respectively, for 10 micrograms Cd/g artificial soil exposure. The distribution of cadmium was examined using whole body autoradiography, tissue distribution, and subcellular localization. Cadmium tissue distribution was exposure-dependent, while cadmium subcellular localization apparently was not exposure-dependent. Acid-soluble thiol levels, examined as an index of cadmium exposure, were too variable in nonexposed earthworms to serve as an indicator of cadmium exposure.