Several different arrangements have been described for increasing the response requirements for reinforcement using the label "progressive-ratio schedule." Under the original progressive-ratio schedule, the response requirement is increased after each reinforcer. Subsequently, arrangements have been used in which the number of required responses increases following multiple reinforcers at a single response requirement or between sessions. Following an assessment of the different types of contingencies that result from such progressive response requirements and the labels used to describe them, a set of descriptive labels is suggested for these different types of progressively increasing response requirements. (Contains 1 figure and 1 footnote.)