With DTPA as a comparison, the siderophore analogue 3,4,3-LIHOPO has been examined for its ability to remove 238Pu and 241Am from the rat after subcutaneous (s.c.) and intramuscular (i.m.) injection of about 200 Bq of each actinide (0.3 ng Pu, 1.6 ng Am). After the s.c. deposition of 238Pu and 241Am, both ligands were more effective after local administration than (in decreasing order) their repeated interperitoneal (i.p.) injection, single i.p. injection and continuous infusion. Dosages of 3 mumol kg-1 of 3,4,3-LIHOPO were at least as effective as 30 mumol kg-1 DTPA after each mode of administration. The most effective regimen of those investigated for s.c. 238Pu and 241Am involved local administration of 30 mumol kg-1 of 3,4,3-LIHOPO at 30 min followed by i.p. injections at 6 h, 1, 2 and 3 day. By day 7 after exposure, the amounts of 238Pu and 241Am retained in the body were 2 and 7% of those in controls, respectively and 10 and four times less than when DTPA was administered using the same regimen. The ligand 3,4,3-LIHOPO was more effective for 238Pu and 241Am after their i.m. injection. This was attributed to the greater retention of these actinides at the wound site (97 versus 67%) when treatment commenced. After a single local injection of 30 mumol kg-1 at 30 min, the amounts of 238Pu and 241Am retained in the body at 7 day were 0.9 and 0.8% of controls. These values were 34 and 27 times less than after local and repeated i.p. injections of DTPA at dosages of 30 mumol kg-1. It is concluded that the administration of 3,4,3-LIHOPO represents potentially a most significant advance in the treatment of wound contamination by 238Pu and 241Am by chelating agents.