Schistosomes rely on host hemoglobin (Hb) degradation for acquiring essential amino acids for growth and sexual maturation. Proteases involved in Hb catabolism are therefore considered as a priori targets for developing antischistosomal drugs. These peptidases belong either to cysteinyl or aspartyl mechanistic classes. At this moment, the only aspartyl protease (AP) gene identified in Schistosoma mansoni (SmCD1) encodes a 41 kDa mature enzyme that is homologous to mammalian cathepsin D. Nevertheless, transcriptome analysis of several life cycle stages of the parasite indicates that other AP genes may exist. Hence, this work aims to investigate the protein complement of the still uncharacterized AP gene family in S. mansoni (SmAP). Firstly, we have thoroughly surveyed the publicly available S. mansoni EST database to sort out AP transcripts expressing different members of the SmAP gene family. It was found that at least 5 and up to 6 SmAP genes are expressed throughout the parasite life cycle. In order to profile the APs expressed in adult worms, parasites were disrupted in a Turrax homogenator and proteins were extracted in PBS containing CHAPS. Using class-specific inhibitors, it could be demonstrated that APs are responsible for 40% of the hemoglobinolytic activity displayed by adult worm extracts (AWE) at pH 3.5. In Western blots using anti-proSmCD1 serum five bands with molecular mass within 33-58 kDa were detected with the major reactive species migrating at 47 kDa. On the other hand, electrophoretics experiments carried out with the photo-affinity fluorescent label TFMPD-Lys(Cy3)-Val-Val-Sta-OH [TFMPD = 4-(3-trifluoromethyl)-phenyldiazirine] revealed, in total extract of the parasite, two species with 36 and 41 kDa. In order to isolate the AP fraction from the AWE, the later was extensively dialyzed against equilibrating buffer at pH 3.5 and the soluble proteins applied to a pepstatin A-agarose column. As observed by immunoblotting, the SDS-PAGE analysis of the retained proteins, revealed a complex pattern with bands ranging from 30-60 kDa. In summary, our results confirm the existence of other SmAPs in adult worms distinct from SmCD1. Currently, we are engaged in the mass spectrometric identification of the SmAP family members detected as affinity-labeled spots in 2D–PAGE of AWE.