We investigate the effect of unintentional disorder on the pass-band capabilities of a GaAs-Al(x)Ga(1-x)As superlattice with Gaussian modulated Al mole fraction. We prove that if fluctuations of vertical disorder can be kept below two monolayers the pass-band filter capabilities are not severely degraded. In addition Al fluctuation as encountered in typical molecular beam epitaxy growth conditions does not degrade the filter capabilities of the Gaussian superlattice. We introduce a new model to deal with lateral disorder and prove that in a molecular beam epitaxial growth process lateral disorder effects are negligible as compared with the vertical disorder ones.