The extraction of iron(II) and iron(III) was studied with long-chain 4-acyl-5-pyrazolones and the corresponding l-phenyl-l,3-(cyclo)alkanediones, and the extraction parameter pH0·5and logKexwere determined. 4-Acyl-5-pyrazolones are able to extract iron(H) as well as iron(III) from stronger acid solutions than 1-phenyl-I,3-(cyclo)alkanediones. The composition of iron(II) complexes is ML2, but the oxidation of iron(II) must be prevented by ascorbic acid. Iron(III) is extracted as ML3species. Iron can be separated from nickel, zinc, and cadmium by means of the studied compounds. The extraction isotherms of these metals with l-phenyl-3-methyl-4-(2-ethylhexanoyl)-5-pyrazolone were determined.