This experiment examined the relationship between two qualitatively different reinforcers and the parameters of a quantitative model of reinforced responding, referred to as the response‐strength equation or the Herrnstein equation. A group of rats was first food deprived and later water deprived. An 11.5% sucrose solution served as the reinforcer in the food‐deprivation condition, and water was the reinforcer in the water‐deprivation condition. Each experimental session consisted of a series of seven variable‐interval schedules, providing reinforcement rates that varied between 20 and 1,200 reinforcers per hour. The response rates increased in a negatively accelerating function in a manner consistent with the response‐strength equation. This equation has two fitted parameters,kandRe. According to one theory, thekparameter is a measure of motor performance, andReis indicative of the relative reinforcement efficacy of the background uncontrollable sources of reinforcement in relation to the experimentally arranged reinforcer. In this study,kdid not change as a result of the different reinforcers, butRewas significantly larger in the sucrose‐reinforcement condition. These results are consistent with the interpretation thatkandRemeasure two independent and experimentally distinguishable parameters and provide further evidence that absolute response rate is a function of relative reinforcement rate, as implied by the derivation of the response‐strength equation based on the