For a periodic vector field F, let X ε solve the dynamical systemIn (Set Valued Anal 2(1-2):175-182, 1994) Ennio De Giorgi enquiers whether from the existence of the limit X 0 (t) := lim ε→0 X ε (t) one can conclude that dX 0 dt = constant. Our main result settles this conjecture under fairly general assumptions on F, which in some cases may also depend on t-variable. Once the above problem is solved, one can apply the result to the corresponding transport equation, in a standard way. This is also touched upon in the text to follow.