Explicit expressions for the superadiabatic temperature gradient in th
e interiors of neutron star are derived. We consider the case without
neutron superfluidity and the case with strong neutron superfluidity.
Convection in the core of a neutron star becomes possible if die therm
al fluxes are directed from the center outward and cause variations in
temperature with the local scale not exceeding several kilometers. Co
nvection may arise in the early stages of die evolution of the star [t
less than or similar to (1 - 10(3)) years] prior to the temperature r
elaxation. This effect was not previously taken into account in calcul
ations of neutron-star cooling.