The measurement of feeding motivation is of central importance in the study of the factors which control feeding behaviour. Current behavioural models describing the control of feeding behaviour define feeding motivation as a temporary and reversible brain state induced by both internal and external stimuli which result in the tendency to perform feeding behaviour (for a review see Lawrence et al., 1993). One of the most sensitive methodologies to measure feeding motivation is operant conditioning where an individual is trained to perform an operant response (behavioural work) to obtain food reinforcement. An index of feeding motivation can then be obtained by varying the quantity of behavioural work required to obtain each unit of food reinforcement and observing the subsequent operant responding. However, this methodology is flawed because it requires a feed restricted animal to regularly ingest food during the test which results in feedback, affecting the underlying level of feeding motivation. A possible solution to this problem is the use of a second order schedule of food reinforcement which assesses an animal's feeding motivation without allowing it to ingest food. During a second order schedule an individual is required to express an operant response for the repeated presentation of a conditioned stimulus (CS) which has previously been associated with the delivery and ingestion of food, with the schedule terminating with food reinforcement. Using this schedule the quantity of behavioural work required per unit food reinforcement could be gradually increased such that a measure of feeding motivation could be obtained in the period prior to the terminal food reinforcement. Therefore, the aim of this study was to investigate whether the CS presented within a second order schedule had reinforcing properties which were linked to the level of feeding motivation. The experiment formed a part of a larger study which had the ultimate objective of developing a methodology to measure feeding motivation without allowing an individual to ingest food.