Misuse of prescription anxiolytic and sedative medication is a widespread phenomenon in Canada and a topic of increasing concern among health care providers. While anxiolytics and sedatives have important therapeutic uses in the treatment of anxiety and insomnia, these substances have psychoactive properties that render them vulnerable to misuse. Understanding the correlates and contexts of misuse is essential for developing targeted treatment and prevention strategies. This dissertation is comprised of a series of four studies conducted with adults in the Halifax Regional Municipality, recruited from the community and from a local substance use disorder treatment program. Study 1 investigated misuse of anxiolytics and sedatives among currently prescribed users of these medications in the general community. Misuse and diversion were associated with a more extensive history of other substance use and with personality dimensions, including hopelessness and impulsivity. Study 2 investigated motives for misuse among non-prescribed anxiolytic and sedative users recruited from the community. This study also included non-prescribed stimulant medication users to facilitate comparisons across differing classes of psychiatric medications. Non-therapeutic motives were associated with substance use history and, for anxiolytics and sedatives, with the personality dimension sensation-seeking. Study 3 involved an analysis of prescription regimens and misuse among all participants of Studies 1 and 2 who had ever held a prescription for an anxiolytic or sedative. Misuse of benzodiazepine anxiolytics and sedatives was more frequent than that of non-benzodiazepines, but was unrelated to prescription regimen. Study 4 examined the misuse of quetiapine, an atypical antipsychotic medication with anxiolytic and sedative effects, among clients of a methadone maintenance program. Misuse of quetiapine was widespread, but was typically associated with therapeutic motives. Quetiapine misuse was linked with a history of misusing other anxiolytic and sedative drugs. Collectively, these studies provide evidence that anxiolytic and sedative misuse is a heterogeneous phenomenon encompassing varying patterns of use and motives for misuse. Furthermore, these investigations suggest that anxiolytic and sedative misuse is linked to individual-level and medication-related variables. By providing a more comprehensive characterization of this important public health issue, these findings have practical implications in both clinical and research contexts.