  I discuss the possibility of production of high energy cosmic tau neutrinos
($E \geq 10^{6}$ GeV) in an astrophysical site 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 tau neutrinos through double
shower events in new km$^{2}$ surface area under water/ice neutrino telescopes.
