The reactions of triarylalkylarsonium acetates with CuI and AgI in the presence of excess potassium thiocyanate yield the corresponding triarylalkylarsonium thiocyanato(N)iodocuprates(I) and -argentates(I). The composition, structure, and thermal behavior (in the range 20 31000oC) of these compounds were studied by chemical analysis, IR spectroscopy, conductometry, and differential thermal analysis.Tetraalkyl(aryl)arsonium halides are excellent precipitants for both relatively simple [1] and complex [2,3] anions. In this connection, it was suggested [4] that quaternary ammonium salts could be successfully used as reagents for quantitative determination of some elements capable of forming anionic complexes. The reactions of soluble arsonium salts with anionic complexes containing different acido ligands were not studied previously. In this study we prepared mixedligand anionic complexes of Cu(I) and Ag(I) with quaternary arsonium cations and examined their structure and thermal behavior in the range 20 31000oC.