Efforts are being undertaken to control tick infestations that cause important economic losses. A cathepsin L-like endopeptidase of Boophilus microplus was expressed in Escherichia coli; the recombinant enzyme was capable of hydrolysing gelatin, tick vitellin and bovine haemoglobin. In this paper we focus on the expression and local of synthesis of this enzyme in the tick. RT-PCR experiments showed that this endopeptidase is transcribed in the gut of partially engorged tick females. In immunoblotting, polyclonal antibodies against the recombinant enzyme reacted with proteins of larvae older than 5 days, of fully and partially engorged female gut. In immunolocalization experiments the enzyme was localized in probable secretory cells of the gut. Based on our findings we postulate that BmCL1 may be involved in haemoglobin degradation in the B. microplus gut. This enzyme may be used as target for the control of this parasite.