Abstract. This article presents sufficient conditions for the positive definiteness of radial functions f (x) = ϕ( x ), x ∈ R n , in terms of the derivatives of ϕ. The criterion extends and unifies the previous analogues of Pólya's theorem and applies to arbitrarily smooth functions. In particular, it provides upper bounds on the Kuttner-Golubov function kn(λ) which gives the minimal value of κ such that the truncated power function (1 − x λ ) κ + , x ∈ R n , is positive definite. Analogous problems and criteria of Pólya type for · α-dependent functions, α > 0, are also considered.