  Vacuum oscillations are considered for the combined solar neutrino
observations, including the Kamiokande II spectrum data and incorporating
theoretical uncertainties and their correlations. Despite the conceptual
difficulty of the fine tuning between the neutrino parameters and the Sun-Earth
distance, 2-flavor vacuum oscillations provide phenomenologically acceptable
solutions. There are allowed regions at 99\% C.L. for $\Delta m^2 = (0.45 -
1.2) \times 10^{-10} \; \mbox{eV}\,^2$ and $\sin^22\theta = 0.6 - 1$; the best
fit solution is $\chi^2 / \mbox{d.f.} = 19.2 / 16$, which is acceptable at 16\%
C.L. Oscillations for sterile neutrinos are, however, excluded by the averaged
data at 99.4\% C.L. The vacuum oscillation solutions predict characteristic
energy spectrum distortions and seasonal variations in Sudbury Neutrino
Observatory, Super-Kamiokande, and BOREXINO. Those predictions are given in
detail, emphasizing that the vacuum solutions are distinguishable from the MSW
solutions.
