Please use this link to access this publication. Abstract Background Previous studies suggest that cannabidiol (CBD) may potentiate or antagonize Δ9-tetrahydrocannabinol’s (THC) effects. The current study examined sex differences in CBD modulation of THC-induced antinociception, hypolocomotion, and metabolism. Methods In Experiment 1, CBD (0, 10 or 30 mg/kg) was administered 15 min before THC (0, 1.8, 3.2, 5.6 or 10 mg/kg), and rats were tested for antinociception and locomotion 15–360 min post-THC injection. In Experiments 2 and 3, CBD (30 mg/kg) was administered 13 h or 15 min before THC (1.8 mg/kg); rats were tested for antinociception and locomotion 30–480 min post-THC injection (Experiment 2), or serum samples were taken 30–360 min post-THC injection to examine CBD modulation of THC metabolism (Experiment 3). Results In...