The residence times of the soluble fractions of beryllium and aluminum in seawater are estimated to be 1500 years or more. These residence times are estimated from a comparison of the annual deposition rates of cosmogenic beryllium-10 and aluminum-26 with the concentrations of beryllium-10 and aluminum-26 in seawater estimated from the specific activities of these radionuclides in an authigenic mineral assembly such as a manganese nodule. These residence times are greater by an order of magnitude than the mean residence times of beryllium and aluminum estimated from the geochemical balance.