Most species rely heavily on olfaction to ensure their survival and reproduction. In addition, the animal’s previous experience has a strong impact on how odors are processed and perceived in order to adapt to a changing environment. While we start to understand how odors are coded and processed by the underlying neuronal circuitry, the impact of modulation and the role of intra-specific variation still remains largely elusive. We are therefore studying how the olfactory circuitry is modulated by previous experience and associative learning as well as analyzing intra-specific variability at the circuit level between different individuals in the fly brain. The vinegar fly Drosophila melanogaster represents a premier model system for studying olfactory processing since it exhibits a stereotyped architecture which is similar to its mammalian counterpart, but is less complex and highly tractable as well as susceptible to genetic manipulations. By exploiting these genetic techniques and linking them to neurophysiological and behavioral methods, we are able to demonstrate that certain olfactory circuits are strongly affected by associative learning and can even be oppositely modulated by aversive and appetitive conditioning. The talk will summarize our recent insights into the modulation and processing strategies of the olfactory circuitry of Drosophila.