  We describe the current situation concerning methods to search for relic
neutrinos from the Big Bang and from all past supernovae (SNs). The most
promising method for Big Bang neutrinos is by the interaction of ultra-high-
energy (UHE) neutrinos. For supernova neutrinos, both Super Kamiokande- and
ICARUS-type detectors will be important to study both nubar_{e} and nu_{e}
fluxes. We also discuss a dedicated supernova burst observatory (OMNIS) being
planned for three sites in the world. We also describe the possible analysis of
the supernova type-II (SNII) neutrinos, including flavor mixing, that might be
carried out in the future.
