BACKGROUND: This study sought to examine the occurrence of the nonmedical use of prescription stimulants (amphetamines and methylphenidate) in a university sample and their associated physical and mental health correlates, including potential relationships with risky sexual practices. METHODS: A 156-item anonymous online survey was distributed via e-mail to a sample of 9449 university students. Current use of alcohol and drugs, psychological and physical status, and academic performance were assessed, along with questionnaire-based measures of impulsivity and compulsivity. RESULTS: A total of 3421 participants (59.7% female) were included in the analysis. 6.7% of the sample reported current/recent nonmedical use of prescription stimulants, while an additional 5.8% reported misuse in the past. Nonmedical use of prescription stimulants was associated with lower grade point averages, and with taking a broad range of other drugs (including alcohol, nicotine, illicit substances, and consumption of caffeinated soft drinks). Nonmedical use of stimulants was also significantly associated with impulsivity (Barratt scale), prior treatment for substance use problems, and elevated occurrence of disordered gambling, post-traumatic stress disorder, and anxiety; but not depression symptoms or binge-eating disorder (though it was associated with using drugs to lose weight). The relationship with probable attention-deficit/hyperactivity disorder (ADHD) on screening was not significant but was numerically elevated. Finally, those using nonmedical prescribed stimulants were significantly more sexually active (including at a younger age), and were less likely to use barrier contraception. CONCLUSIONS: Nonmedical use of prescription stimulants is common in young adults and has profound public health associations including with a profundity of other drug use (licit and illicit), certain mental health diagnoses (especially gambling, anxiety, and post-traumatic stress disorder ), worse scholastic performance, and riskier sexual practices. The majority of people with nonmedical use of prescription stimulants do not have ADHD, and its link with current ADHD symptoms was less marked than for certain other disorders. Clinicians should screen for the misuse of prescription stimulants as they may be associated with a range of problematic behaviors. Risk of diversion (which may be higher for those living in shared accommodation and those with substance use disorder history) merits careful assessment before prescribing stimulant medication.