  We study neutrino conversions in a recently envisaged source of high-energy
neutrinos (E \geq 10^6 GeV), that is, in the vicinity of cosmological Gamma-Ray
Burst fireballs (GRB). We consider the effects of flavor and spin-flavor
conversions and point out that in both situations, a some what higher than
estimated high energy tau neutrino flux from GRBs is expected in new km^2
surface area under water/ice neutrino telescopes.
