The synergistic extraction of trivalent Am, Cm, Cf and Eu with mixtures of 1—phenyl—3—methyl 1—4— trifluoroacetyl pyrazolone—5 ( HPMTFP) and a crown ether dicyclohexano—18—crown—6 (DCH18C6) or monobenzo—15—crown—5 ( B15C5) has been studied in chloroform. With DCH18C6 the synergistic species extracted are M(PMTFP)3 (HPMTFP) (DCH18C6) where N = Am, Cm and Eu and Cf ( PMTFP)3. (DCH18C6) whereas with B15C5 the species are M( PMTFP) 3.n( B15C5), n being 1 or 2 for all these metal ions. The possibility of high coordination numbere for theee metal ions in the above syeteme and the probable reaeone for the anbormel order of synergistic constants namely K2≫81 have been discussed.