Abstract: In repeating and extending the syntheses of organo-arsenic polytungstates,we found that the "Degradation Method",taking sodium metatungstate as the starting material,was much more profita-ble.The known compound (CN₃H₆)₅[(C₆H₅As)₂W₆O₂₅H]·2H₂O(1) was read-ily reproduced with a high yield.Anew compound (CN₃H₆)₆[(p-OH,m-NO₂C₆H₃As)₂W₆O₂₅](2) was likewise synthesized.This "Degradation Method" using the reaction of sodium metatungstate with organo-anti-monate led to the isolation of four compounds with definite composition although amorphous in appearance.The preparations of organo-arsenic polymolybdates and organo-antimony polymolybdates were also studied and six new organo-arsenic polymolybdates were isolated: (CN₃H₆)₅[(C₆H₅As)₂MoO₂₅H]H₂O(3),(CN₃H₆)₄[(n-C₃H₇As)₂Mo₅O₂₁]·2H O (4),(CNH)₄[(n-C₃H₇As)₂Mo₆O₂₄](5),Cs₂[(CH₃)₂AsMo₄O₁₅H](6),(NH₄)₆[(P-OH,m-NO₂C₆H₃·As)₂Mo₆O₂₅](7),and (CN₃H₆)₆[(p-OH,m-NO₂C₆H₃ As)₂Mo₆O₂₅](8).No definite corresponding organo-antimony polymo-lybdate with definite composition has been isolated yet.