First published in 1986. This is Volume V of six in a series on Quantitative Analyses of Behavior. Quantitative analysis now generally refers to the fact that theoretical issues are represented by quantitative models. An analysis is not a matter of fitting arbitrary functions to data points. The volumes in the present series have been written for behavioral scientists. Those concerned with issues in the study of how behavior is acquired and then allocated in various environments-biologists, psychologists, economists, anthropologists, and other researchers, as well as graduate students and advanced undergraduates in those areas-should find volumes in this series to be state-of the-art readers and reference works. Each volume of the series examines a particular topic that has been discussed at the annual Symposium on Quantitative Analyses of Behavior held at Harvard University. This volume, V, addresses the topic of how reinforcement value is affected by delay and intervening events. Self-control studies are also presented and discussed.