Aims: The study was designed to investigate the acute effects of ingested tetrahydrocannabinol (THC) on auditory function. Methods: Eight male subjects (aged 22–30 years), who had previous experience of cannabis use, took part in this study. They performed air conduction pure tone audiometry in both ears over 0.5–8 kHz. A simple test of frequency selectivity by detecting a 4-kHz tone under two masking noise conditions was also carried out in one ear. Three test sessions at weekly intervals were carried out, at the start of which they ingested a capsule containing either placebo, or 7.5 or 15 mg of THC. These were administered in a randomized cross-over, double-blind manner. Auditory testing as described above was carried out 2 hours after ingestion. Blood samples were also obtained at this time point and assayed for ¢9-and 11-OH-THC levels. Results: No significant changes in threshold or frequency resolution were seen with the dosages employed in this study. Conclusions: This suggests that THC at the plasma levels attained in this study does not have a profound effect on the processing of elementary stimuli by the auditory pathway.