Nonmedical prescription stimulant use (NMPSU) is a rising trend among college-age adults (18-25 years old). Survey research has identified several reasons for use, including enhancing cognitive, athletic, and social performance. Less is known about how relative reinforcing value differs based on the self-reported reasons for use. The commodity purchase task (CPT) is used to assess demand for substances such as alcohol and cigarettes and has been extended for NMPSU among college student users. However, this work has not been replicated for NMPSU or expanded to determine how reason for use affects drug demand. The aim of this study was to develop a novel functional purchase task (FPT) to measure demand for preferred stimulant-like drug effects (e.g., focus, academic achievement, energy). Undergraduate students (n = 116) recruited from two universities who endorsed lifetime NMPSU completed five hypothetical stimulant purchase tasks, one for stimulant medication and four based on their ordinal ranking of eight possible reasons for stimulant use. Results support using a CPT to measure the reinforcing value of prescription stimulants and found demand predicts past year NMPSU, but not other variables associated with use. Furthermore, there are multiple reinforcing functions of NMPSU among college students, and more preferred reasons for use corresponded with higher demand intensity and inelasticity on the FPT at the aggregate level but less so at the individual participant level. These results suggest the need for further work exploring the utility of a functional approach to measure demand as reinforcing value. (PsycInfo Database Record (c) 2022 APA, all rights reserved).