Recently published rates of elimination of radium (in percentage of contemporary body content per year) demonstrated that human radium cases with low body contents lost radium more rapidly than predicted by the ICRP Publication 20 retention equation. In ICRP Publication 20, the apposition and resorption rate in compact bone is defined as 2.5% y−1, but in the derivation of the retention equation for radium a value of only 1.5% y−1 was used. In the present work, the retention equation was reevaluated by using the rate of 2.5% y−1. The revised equation was a good fit to the data for measured values of the body content of radium from environmental levels of radium in food and water. The equation also described the observed rate of loss of radium at long times after deposition for radium cases with low measured body burdens.