The cluster autocorrelation function ξc and the galaxy-cluster cross correlation ξgc are used to test the biased structure formation for scale-free spectra P(k)∝kn. Following Kaiser (1984), we assume that rich clusters form only at higfr density regions with the matter distribution represented by a Gaussian random field. Then, the correlation ξ of two regions with characteristic scales R1 and R2 lying above the thresholds v1 and v2 (δ ≡ νσ), is given by the expression for the bivariate Gaussian where z(r) is the coviance function, i.e. and is the correlation of the matter distribution Gaussian filtered on the comoving scales R1 and R2. From the previous equations, one can obtain for P(k)∝ kn, τ≪1 and large r a powers-law form either for ξc or ξgc. Moreover, the amplification factor Ac - gc ≡ ξc/ξgc is