We consider a second order differential operator A on an open and Dirichlet regular set Ω ⊂ R d (which typically is unbounded) and subject to nonlocal Dirichlet boundary conditions of the formHere, µ : ∂Ω → M (Ω) takes values in the probability measures on Ω and is continuous in the weak topoly σ(M (Ω), C b (Ω)). Under suitable assumptions on the coefficients in A , which may be unbounded, we prove that a realization Aµ of A subject to the nonlocal boundary condition, generates a (not strongly continuous) semigroup on L ∞ (Ω). We establish a sufficient condition for this semigroup to be Markovian and prove that in this case, it enjoys the strong Feller property. We also study the asymptotic behavior of the semigroup.2010 Mathematics Subject Classification. 47D07, 60J35, 35B40.