The power spectrum of the distribution of clusters of galaxies in the northern and southern galactic hemispheres has been evaluated. Corrections have been applied for the smoothing effect, and for the Poisson noise. The effects of incompleteness of data and observational errors have been investigated. The cluster spectrum has been transformed to galaxy and matter power spectra. Data suggest that the power spectrum has an index - 2 <= n <= - 1 on intermediate scales; on very large scales the spectrum is consistent with the Harrison-Zeldovich index n = 1. The transition from the Harrison-Zeldovich index to a lower index occurs at the scale λ_t_ ~ 150+/-50 h^-1^ Mpc. Direct comparison of the samples used and power-spectrum analysis suggest that our samples approach the size of fair samples of the Universe.