  We investigate temporal variations of the solar neutrino flux in 1970-1997.
The periods of 11, 5 and 2 years have been found in the variations of the
neutrino flux. The results indicate that a periodicity close to 5 years is the
most significant in the data from both the Homestake and GALLEX experiments.
Two groups of the solar activity indices have been distinguished regarding
their interconnection with the neutrino flux series. The first group contains
the indices showing predominantly 11-year period, while a periodicity at
approximately 5 years is observed in the second group. The correlation
coefficients between the neutrino flux and indices from the first group are
negative, with their module not exceeding 0.5. The second group is
characterized by positive correlation with the neutrino counting rates with
coefficients not lower than 0.6. A discussion of findings is presented.
