  We formulate a conjecture on the number of integral points of bounded height
on log Fano varieties in analogy with Manin's conjecture on the number of
rational points of bounded height on Fano varieties. We also give a prediction
for the leading constant which is similar to Peyre's interpretation of the
leading constant in Manin's conjecture. We give evidence for our conjecture by
proving it for toric varieties. The proof is based on harmonic analysis on
universal torsors.
