We work in the context of ω-stable theories. We obtain a natural, algebraic equivalent of ENI-NDOP and discuss recent joint proofs with Shelah that if an ω-stable theory has either ENI-DOP or is ENI-NDOP and is ENI-deep, then the set of models of T with universe ω is Borel complete.

Let T be an uncountable, superstable theory. In this paper we prove Theorem A. If T has finite rank, then I(|T|, T) ≥ ℵ0. Theorem B. If T is trivial, then I(|T|, T) ≥ ℵ0.

In [R. Vaught, Denumerable models of complete theories, in: Infinitistic Methods, Pregamon, London, 1961, pp. 303–321] Vaught conjectured that a countable first order theory has countably many or 20 many countable models. Here, the following special case is proved.