Abstract: The invention relates to a method for classification of a sample on the basis of spectral data, a method for creating a database and a method for using this database, and corresponding computer program, data storage medium and system. The method comprises: a) obtaining at least two sets of first spectra for use as reference spectra, each set comprising spectra of reference samples belonging to the same class; b) determining for each of the reference spectra the value of the same at least one quantity related to a spectral feature; c) associating a probability to different values of the quantity on the basis of the determined values; d) obtaining a spectrum from the sample and determining the value of the same at least one quantity of this spectrum; and e) calculating on the basis of the probabilities and the value of the quantity for the obtained spectrum for each of said at least two classes a probability that the sample belongs to that class.