Neutrino Conversions in Active Galactic Nuclei

I discuss the possibility of production of high energy cosmic neutrinos (E \geq 10^{6} GeV) in cores of active galactic nuclei and study some of the effects of neutrino mixing on their subsequent propagation. I also discuss the prospects for observations of these high energy cosmic neutrinos in new km^{2} surface area underwater/ice neutrino telescopes.