The essential oil of catmint, Nepeta cataria L., was hydrogenated to yield an oil enriched in dihydronepetalactone (DHN) diastereomers, termed. This material was used for the preparation of liquid alcohol–based and lotion formulations. The efficacy of these formulations as repellents was tested after application to human test subjects at two locations in the United States: Maine and Florida. In Maine, data on repellency of the hydrogenated catmint oil formulations toward black flies (Simulium decorum Walker) and mosquitoes (primarily Aedes intrudens Dyar) were obtained. In these tests, protection from black flies was conferred for 6 h or more with all formulations, and both liquid and lotion formulations at 15 wt% active ingredient gave complete protection for 7.5 h. All formulations conferred protection from mosquitoes for >4 h, with the best (15 wt% lotion) giving >8 h of complete protection. In Florida, data on repellency toward a mixed population of mosquitoes indicated that all formulations conferred protection for >4 h, with the 15 wt% lotion giving >6 h complete protection from bites.