Chemosensory proteins are a class of small (10-15 kDa), soluble proteins characterised for the first time by Angeli et al. (1999) as secreted into the sensillar lymph of insect chemosensory sensilla. Some members of CSPs were already discovered in Drosophila, and other insects, although no clear link with olfactory or gustatory function was assigned. In the last years CSPs were found in insect contact and olfactory sensilla, but other members showed peculiar functions. In Apis mellifera one member was found to be involved in larval development and in Blatta a CSP is involved in leg regeneration. Binding activity of volatile compounds has been described in a similar way as in other group of soluble sensillar proteins, called Odorant binding proteins or OBPs. CSPs do not share sequence similarity with OBPs and are characterized by only 4 conserved cysteines, where insect OBPs have 6 conserved cysteines.