We prove existence and, under an additional assumption, uniqueness of an evolution system of measures (ν t ) t∈R for a stochastic differential equation with time dependent dissipative coefficients. We prove that if P s,t denotes the corresponding transition evolution operator, then P s,t ϕ behaves asymptotically as t → +∞ like a limit curve (which is independent of s) for any continuous and bounded "observable" ϕ.