Contraindications to mefloquine use include a history of certain prevalent neuropsychiatric disorders, which are thought to increase the risk of severe adverse events including anxiety, paranoia, depression, hallucinations, psychosis, and possibly suicide. Within the US military, the continued availability and use of mefloquine is subject to administrative policies dating to 2002 that require clinicians to exercise added caution during prescribing. This analysis was performed to quantify the effectiveness of these policies in ensuring health care provider compliance with package insert prescribing guidance. A previously identified cohort consisting of 11,725 active duty US military personnel, among whom 1127 (9.6%) had contraindications to mefloquine use identified through medical surveillance and pharmaceutical databases, was examined to identify individuals receiving prescriptions for mefloquine in the 45 days prior to a combat deployment in 2007. Among the 11,725 cohort members, 4505 (38.4% of the cohort) received a prescription for mefloquine. Among the 1127 cohort members with contraindications, 155 (1.3% of the cohort) were prescribed mefloquine, comprising 13.8% of those with contraindications. Despite the longstanding administrative policies meant to reduce such events, approximately one in seven individuals with neuropsychiatric contraindications received a prescription for mefloquine prior to a recent combat deployment, significantly increasing the risk of subsequent adverse events. Given the prevalence of neuropsychiatric disorders among US military personnel and the continued availability of mefloquine, additional study is recommended to describe and quantify the nature and extent of mefloquine-associated adverse events experienced among this group.