Essential oils of Hyptis suaveolens (Lamiaceae), Croton roxburghii (Euphorbiaceae), and Litsea cubeba (Lauraceae) were tested in the field near Vientiane city, Lao PDR, on humans for repellent activity against mosquitoes. Landing mosquitoes were collected and later identified. The most abundant mosquitoes captured belonged to the genera Armigeres, Culex, and Aedes. All the plant oils tested at concentrations of 1.7 µg/cm², 3.3 µg/cm², and 6.3 µg/cm² were significantly more mosquito repellent than the negative control. Croton oil was significantly repellent against mosquitoes of the three genera at the highest (6.3 µg/cm²) concentration tested. Litsea oil was significantly repellent against Annigeres at all (1.7 µg/cm², 3.3 µg/cm², and 6.3 µg/cm²) concentrations tested. Hyptis oil was significantly repellent against Armigeres at 3.3 µg/cm² and 6.3 µg/cm² and against Culex at 1.7 µg/cm²and 6.3 µg/cm². The oils were analyzed for chemical content of volatiles, mainly terpenes. Main constituents were β-pinene, sabinene, and 1,8-cineol from oils of the green parts of H. suaveolens; α-pinene, β-pinene, and α-phellandrene from fresh bark of C. roxburghii; and α-pinene, β-phellandrene, sabinene, and 1,8-cineol from fresh fruits of L. cubeba.