The essential oil of catnip, Nepeta cataria (Lamiacae) was evaluated for behavioral effects on two populations of subterranean termite, Reticulitermes flavipes (Kollar) and R. virginicus (Banks) (Isoptera: Rhinotermitidae). The catnip essential oil contained ≈36: 64 E,Z-nepetalactone and Z,E-nepetalactone, respectively. The time to 50% dissipation (DT₅₀) of the isomers in sand was dependent on dose, and ranged from 5.7 to 12.6 d for the E,Z-isomer and 7.7–18.6 d for the Z,E-isomer. For R. flavipes, the 24-h topical LD₅₀ value was ≈8200 μg/g termite. The 24-h fumigation LC₅₀ value for R. flavipes was between 36 and 73 μg/ml air, and the 7-d fumigation LC₅₀ value was between 14 and 36 μg/ml air. Exposure of R. virginicus to treated sand resulted in a 24-h LC₅₀ value (95% F.L.) of 84 (67.6, 112) μg/cm² and a 7-d LC₅₀ value of 21.1 (16.4, 26.8) μg/cm²; for R. flavipes these values were 63.2 (53.7, 73.9) and 44.4 (34.6, 58.1) μg/cm², respectively. Vertical tunneling through treated sand was eliminated at 500 ppm for R. virginicus and at 250 ppm for R. flavipes. Horizontal tunneling was stopped at 250 ppm for R. virginicus and reduced at doses above 250 ppm for R. flavipes. Although tunneling ceased in these tests, mortality was not high, indicating that the termites avoided the treated sand. Efficacy of catnip oil was equivalent to other monoterpenoids reported in the literature.