AIM: We aimed to assess the analgesic efficacy, pharmacokinetics, tolerability and safety of a single dose Δ9-THC in patients with chronic abdominal pain resulting from chronic pancreatitis (CP). METHODS: This was a randomized, single-dose, double-blinded, placebo-controlled, two-way cross-over study in patients suffering from abdominal pain as result of CP (n = 24), post hoc subdivided into opioid and non-opioid users. Δ9-THC (8 mg) or active placebo (5 mg / 10 mg diazepam) was administered orally in a double dummy design. RESULTS: No treatment effect was shown for delta VAS pain scores after Δ9-THC compared with diazepam. Δ9-THC was well absorbed with a mean tmax of 123 min. No significant differences were found between Δ9-THC versus diazepam for alertness, mood, calmness or balance. Feeling anxious and heart rate were significantly increased after Δ9-THC compared with diazepam. Most frequently reported adverse events (AEs) after Δ9-THC administration were somnolence, dry mouth, dizziness and euphoric mood. CONCLUSIONS: A single dose Δ9-THC was not efficacious in reducing chronic pain resulting from CP, but was well tolerated with only mild or moderate AEs. The PK results in CP patients showed delayed absorption and an increased variability compared to healthy volunteers.