In 1954, Hirzebruch asked which linear combinations of Chern numbers are topological invariants of smooth complex projective varieties. We give a complete answer to this question in small dimensions, and also prove partial results without restrictions on the dimension.As the right-hand side takes on only finitely many values, the same is true for c 4 1 , and then for c 2 1 c 2 as well.Remark 2. Pasquotto [9] recently raised the question of the topological invariance of Chern numbers of symplectic manifolds, particularly in (real) dimensions 6 and 8. Our results for Kähler manifolds, of course, show that Chern numbers of symplectic manifolds are not topological invariants. In the Kähler case, we have used Hodge theory to argue that the variation of Chern numbers is quite restricted, often to finitely many possibilities. It would be interesting to know whether any finiteness results hold in the symplectic non-Kähler category.