The effect of a complexon therapy scheme including early (in 1 h) administration of Na3Ca DTPA and subsequent (in 1 day) administration of Na3Zn DTPA or Na3Ca DTPA at a dose of 25 mu Cimol/kg/day by three 2-week courses (5 times a week) with 2-week interruptions was studied in experiments on 541 male rats after intraperitoneal administration of 239Pu citrate complex (95 kBq/kg). The treatment resulted in a 3-fold lessening of the content of 239Pu and absorbed doses in the skeleton, a significant prolongation of the mean survival time (MST) from 452 to 593 days (Na3Zn DTPA) and 643 days (Na3Ca DTPA), and in a decrease of the osteosarcoma incidence from 76.4 to 32.6-41.2%. The ratio of osteosarcomas per 1 Gy retained in rats (0.076-0.083%) did not differ from that in untreated animals (0.067%) and varied within the ranges of established values (0.072-0.119%). The involvement of Na3Zn DTPA in the therapeutic scheme prolongs the MST of rats to a somewhat lesser degree than Na3Ca DTPA. No negative effects of Zn DTPA therapy were revealed.