  We propose a two-dimensional exciton model showing the possibility of
two-exciton pairing in cuprates, both in singlet and in triplet states. The
former is assumed to be responsible for the superconductivity and the latter
for the unusual normal state properties. The ground state is found to be a
projection of the Bose condensation of N/2 mobile bosons with a \eta projection
operator which is a generalization of the Gutzwiller projection operator. The
phase diagram of the model shows insulator-superconductivity and
superconductivity-metal transitions with doping.
