  We discuss four approaches to the determination of absolute neutrino mass.
These are the measurement of the zero-neutrino double beta decay rate, of the
tritium decay end-point spectrum, of the cosmic ray spectrum above the GZK
cutoff (in the Z-burst model), and the cosmological measurement of the power
spectrum governing the CMB and large scale structure. The first two approaches
are sensitive to the mass eigenstates coupling to the electron neutrino,
whereas the latter two are sensitive to the heavy component of the cosmic
neutrino background. All mass eigenstates are related by the $\Delta m^2$'s
inferred from neutrino oscillation data. Consequently, the potential for
absolute mass determination of each of the four approaches is correlated with
the other three, in ways that we point out.
