We study the method of finding conformal maps onto circle domains by approximating with finitely connected subdomains. Every domain D ⊂ Ĉ admits exhaustions, i.e., increasing sequences of finitely connected subdomains Dj whose union is D. By Koebe's theorem, each Dj admits a conformal map fD j from Dj onto a circle domain fD j (Dj ). Assuming fD j → f , our goal is to find out if f (D) is also a circle domain.We present a countably connected D with an exhaustion (Dj ) so that (fD j ) has a limit whose image is not a circle domain, and a domain Ω with an exhaustion (Ωj ) so that (fΩ j ) has a limit whose image has uncountably many non-point complementary components.On the other hand, we prove that every exhaustion (Dj) of a countably connected D admits a refinement so that the image of the corresponding limit map is a circle domain. Our result extends the He-Schramm theorem on the uniformization of countably connected domains and provides a new proof.