ABSTRACT.    Ticks are blood-feeding ectoparasites of reptiles, birds and mammals including human. As an obligate blood feeders, host blood proteins and especially the most abundant component of the mammalian blood - hemoglobin provide main source of energy crucial for many processes as molting, vitellogenesis etc. Despite its importance, the hemoglobin digestion in ticks is still poorly understood at molecular level. We have searched for the peptidases in the gut of the hard tick Ixodes ricinus, one of the most serious disease vectors in Europe, well-known especially for transmitting the tick borne-encephalitis virus and the spirochette Borrelia burgdorferi, the causative agent of Lyme disease. The screening of gut-specific cDNA by PCR amplification using primers derived from the conserved regions of cysteine and aspartic peptidases resulted in identification of genes coding for cysteine endopeptidases as asparaginyl endopeptidase (legumain-like) from CD clan designated as IrAE, cathepsin B1, B2 and L, dipeptidyl peptidase cathepsin C and the aspartic peptidase cathepsin D. The tissue expression analysis by RT PCR revealed that all peptidases are expressed in the tick gut and it was also confirmed by the substrate/inhibitor based screening of endogenous peptidolytic activities in the tick gut homogenate. Although we have identified the key players of the tick blood digestion, we still know very little about their individual contribution to the hemoglobinolysis and their mutual interplay within this network/cascade.