Pyrazolones and isoxazolones have been found to be promising extractants for metal ions, particularly from strong acidic media and in the presence of complexing anions. Extraction constants (log k(ex)) in toluene medium at 25-degrees-C for PuX4 species, where X = 1-phenyl-3-methyl-4-acetyl-pyrazolone-5 (HPMAP), 1-phenyl-3-methyl-4-benzoyl-pyrazolone-5 (HPMBP), or 1-phenyl-3-methyl-4-(3:5-dinitrobenzoyl)pyrazolone-5 (HPMDP), are determined as 11.35 +/- 0.04, 12.89 +/- 0.03, and 12.73 +/- 0.02, respectively. These values are comparable to the corresponding value for 3-phenyl-4-benzoyl-5-isoxazolone (HPBI) and several order of magnitude larger than that for 2-thenoyltrifluoroacetone (HTTA). A systematic study is carried out to investigate the extraction behavior of these beta-diketones toward plutonium present in the analytical waste solution obtained during the determination of uranium in a (U, Pu) fuel sample by the Davies Gray method. Whereas 0.3 M HPMBP extracts >85% of the plutonium present in a single step, maximum extraction observed with other reagents is much less than 0.1% HTTA, 0.3% HPMAP, and 2.5% HPBI. The extraction of plutonium increases with different diluents in the order n-dodecane < n-hexane < CHCl3 < CCl4 < toluene. Extracted plutonium is quantitatively stripped with either 10 M HNO3 or 1:1 HCl + 0.1 M hydroquinone.