The honeybee (Apis mellifera) is a model organism for the study of learning and memory formation and its underlying mechanisms. Honeybees have a rich behaviour that can be studied in the field as well as in the laboratory. In the latter case, olfactory conditioning of the proboscis extension response (PER) has been intensively studied with respect to the neuronal and molecular mechanisms underlying acquisition and memory formation. Quite a lot is known about the neuronal pathways of both the unconditioned and the conditioned stimulus, and molecular mechanisms that lead to memory formation have been identified. In particular, the role of the cAMP-protein kinase A pathway in memory formation has been analysed. Present knowledge about the molecular basis of memory formation is outlined here. The role of the cAMP-dependent signalling cascade in memory formation is summarised and the activation of this pathway by non-associative and associative learning is discussed.