The protein and peptide composition of medicinal leech salivary gland secretion (SGS) was analyzed in preparations obtained in July from three species--Hirudo verbana, H. medicinalis, and H. orientalis. Two-dimensional electrophoresis (molecular mass 10-150 kD and pI 3-10) revealed no distinctions in the distribution of over 100 silver-stained proteins. Differences were noted only in intensity of 10 protein spots at 30-90 kD and pI 4.7-7.5. Mass spectrometric profiling of SGS of the three leech species using the Zip-Tip/golden chip scheme and cation-exchanging chips CM-10 revealed over 50 components in SGS of each of the three leech species. It was noted that 30-40% of the individual masses of the SGS of each leech species fall within the masses present in SGS of at least one of the two other species. This rather small part of the total mass may be indicative of a high polymorphism of amino acid sequences or a high frequency of posttranslational modifications of the SGS proteins and peptides. Calculation of Jacquard's coefficient showed that H. medicinalis and H. orientalis are closest to each other in SGS composition, which is consistent with data in the literature on the phylogenetic relationship between these two species of medicinal leech. Comparison of detected molecular masses with those of six known biologically active compounds produced by medicinal leeches revealed their uneven distribution in SGS of each of the three medicinal leech species. This opens prospects for using certain species of medicinal leech for targeted therapy of various pathologies.