A procedure for the treatment of electrophoretic patterns is presented and discussed using SDS-PAGE patterns of whole-cell proteins of lactic acid bacteria as an example. Complex patterns consisting of two vectors of data [molecular weights (MW), and band intensities] with varying length were transformed in a single vector of fixed length consisting of band intensities accumulated in classes of MW by a logistic weighting function. The procedure performed better than a commercial software (Diversity Database) in clustering the patterns.