I shall prove a version of Voiculescu's theorem for ultraproducts. Suppose that C is an ultraproduct of simple C*-algebras, and A is a separable subalgebra of C. Then the double relative commutant of A in C is equal to A. This result is a part of an ongoing joint work with Aaron Tikuisis and Stuart White whose goal is to prove that stably finite nuclear C*-algebras are tracial (even without assuming the UCT; with the UCT this is a recent theorem of Tikuisis, White and Wilhelm Winter).