[en] The excretion history of plutonium workers who acquired body burdens some 20-30 yr ago indicates that the most precisely known function for excretion (U/I=0.0023Tsup(-0.77), developed for a 138-day excretion period) is not valid 10 yr after uptake. To fulfill the need for a long-term excretion function, the ICRP model of a bone pool of 100-yr half-time containing 45% of the systemic burden has been used as a starting point. For excretion at times less than approximately 1500 days, a series of exponentials has been fit to the power function above. Calculated by the resulting equation, the excretion rate after 10,008 days would be about four times that calculated by the power function. Agreement is +- 36%(σ) with the observed excretion rate from two long-term cases, but there is an urgent need for improvement of the function by application to many additional cases. (author)