Molecular sieve compositions having three-dimensional microporous framework structures of AsO.sub.2, AlO.sub.2, PO.sub.2 and SiO.sub.2 tetrahedral oxide units are disclosed. These molecular sieves have an empirical chemical composition on an anhydrous basis expressed by the formula:mR: (As.sub.w Al.sub.x P.sub.y Si.sub.z)O.sub.2wherein "R" represents at least one organic templating agent present in the intracrystalline pore system; "m" represents the molar amount of "R" present per mole of (As.sub.w Al.sub.x P.sub.y Si.sub.z)O.sub.2 ; and "w", "x", "y" and "z" represent the mole fractions of arsenic, aluminum, phosphorus and silicon, respectively, present as tetrahedral oxides. Their use as adsorbents, catalysts, etc. is also disclosed.