Several studies have shown that the piriform cortex is involved in learning processes and pyramidal cell activity does not only encode the odour quality but is also related to contextual information about past experience and future action. To study how odour-specific patterns in neuronal activity are established we used an odour discrimination go/no go task with water reinforcement for analysing extracellular single cell activity in anterior piriform cortex in freely moving rats. During conditioning single cells responded to different task events. Of the cells 52% participate in odour sampling and 87% were involved in odour discrimination. More than half of the responses to odours were inhibitory responses. Seventeen percent changed their activity for nose-poke only. The activity of 33% was related to reinforcement. Once established the pattern of reaction to the odour was preserved for several days. It is suggested that the anterior part of the piriform cortex is not involved in odour coding only. However, learning-related plasticity was not observed in this area.