Abstract: Titanium-aluminum-silicon-oxide molecular sieves are disclosed having use as molecular sieves and as catalyst compositions in hydrocarbon conversion and other processes. The molecular sieves have a unit empirical formula on an anhydrous basis ofmR: (Ti.sub.x Al.sub.y Si.sub.z)O.sub.2wherein "R" represents at least one organic+ emplating agent; "m" represents the moles of "R" present per mole of (Ti.sub.x Al.sub.y Si.sub.z)O.sub.2 ; and "x", "y" and "z" represent the mole fractions of titanium, aluminum and silicon, respectively, present as tetrahedral oxides. The molecular sieve is useful in separating molecular species having different degrees of polarity and/or kinetic diameters.