The possible applications of multilayer neural networks and the backpropagation algorithm to qualitative analysis and quantitative evaluation of circular dichroism spectra of proteins are discussed. The analysis consisted of three parts: (i) the results of x-ray crystallographic analyses of proteins were sorted out using both symmetric 5- n-5 neural networks ( n = 1, 2, 3, 4) and ‘classical’ cluster analysis. (ii) The x-ray results were used as the learning information in the second step: the network was trained to recognize them from the experimental spectral intensities forming the input layer of the network. (iii) The reverse step (i.e. reconstruction of the spectrum from the structural information) was the final task. The developed combination of the networks forms a unique, internally consisted tool for the biomolecular spectra analysis.