The recent atmospheric neutrino data from Super-Kamiokande  provide strong evidence of neutrino oscillations and therefore of non-zero neutrino mass. These data imply a lower limit on the hot dark matter (i.e., light neutrino) contribution to the cosmological density 0.001. is actually that low, and therefore cosmologically uninteresting, if m() >> m(µ), as is suggested by the hierarchical pattern of the quark and charged lepton masses. But if the and µ are nearly degenerate in mass, as suggested by their strong mixing, then could be substantially larger. Although the Cold + Hot Dark Matter (CHDM) cosmological model with h 0.5, m = 1, and = 0.2 predicts power spectra of cosmic density and CMB anisotropies that are in excellent agreement with the data [96, 49], as we have just seen the large value measured for the Hubble parameter makes such m = 1 models dubious. It remains to be seen whether including a significant amount of hot dark matter in low-m models improves their agreement with data. Primack & Gross [97, 98] found that the possible improvement of the low-m flat (CDM) cosmological models with the addition of light neutrinos appears to be rather limited, and the maximum amount of hot dark matter decreases with decreasing m . For m 0.4,  find that 0.08;  finds more restrictive upper limits with the constraint that the primordial power spectrum index n 1, but this may not be well motivated.