SUMMARYThe acetyl moiety in aspirin (acetyl salicylic acid: ASA) is considered to play a major part in the pathogenesis of ASA‐induced mucosal injury. At equivalent salicylate doses and pH values, the induction of acute gastric mucosal haemorrhagic erosions in rats by ASA and choline magnesium trisalicylate (CMT), a new non‐acetylated salicylate, with and without the potentiating damaging effect of taurodeoxycholic acid (TDCA) were compared. Test solutions were administered byper oralintubation to five groups of fasting Sprague–Dawley rats (n= 24). Gastric mucosa were examined after 4 hours and mucosal injury assessed by a lesion‐scoring system. The incidence and severity (median lesion scores with quartiles) of the lesions were 83% and 13 (7:20) respectively for ASA (128 mg kg−1) compared with 17% and 0 (0:0) for CMT (128 mg kg−1) (P<0.001 andP<0.001). TDCA increased mucosal damage to 100% and 29 (20:34) for ASA compared with 30% and 0 (0:4) for CMT (P<0.001) and P<0.001). Serum salicylate levels (median values of 1.4 for ASA and 1.5 mmol litre−1for CMT) were not significantly different. It is concluded that replacing the acetyl moiety in ASA with choline and magnesium moieties reduces the ASA‐induced mucosal injury, without affecting blood salicylate