In the animal kingdom, the relationship between individuals and the environment is often modulated by chemical communication. In the olfaction of insects, small antennary proteins – such as odorant- and pheromone-binding proteins (OBPs and PBPs, respectively) and chemosensory proteins (CSP)– have been proposed to carry their ligand from the air–fluid interface to the olfactory receptors. Binding experiments and recent structural studies of three PBPs, an OBP and a CSP have illustrated their versatility and ability to accommodate ligands of different shapes and chemical structures. The role of these proteins – as simple transporters or receptor triggers – is still a matter of debate, but some recent data seem to support the latter.