Electron and muon thermal conductivity of dense matter (rho greater th
an or similar to 10(14) g.cm(-3)) in neutron star cores with various n
uclear compositions (n, p, e, mu and possibly hyperons) is calculated.
The effects of nucleon (and/or hyperon) superfluidity are taken into
account. In non-superfluid matter, the main scattering mechanism of el
ectrons and muons is the Coulomb scattering on charged baryons. If the
baryon component of matter is highly superfluid, ee, e mu and mu mu c
ollisions dominate. The results are described by simple analytic expre
ssions valid for a wide class of models of dense matter.