Angiotensin converting enzyme inhibitors could lead to severe diarrhoea related to microscopic colitis. Few of such cases have been reported before and this serious problem, from a widely used class of drugs in hypertension and heart failure, needs to be more recognised. We describe the case of collagenous colitis related to ramipril use in the following case report. A 74-year-old farmer who had a history of triple vessel coronary artery disease was admitted to district general hospital with non-ST elevation myocardial infarction. He had known alcohol-related chronic pancreatitis with chronic diarrhoea as a complication, which was managed with pancreatic enzyme replacement therapy. However, he developed severe worsening of diarrhoea causing bowel incontinence and nocturnal symptoms during his admission to hospital. The explosive and watery nature of diarrhoea with urgency was so troublesome that it delayed coronary revascularisation and lead him to have significant psychological distress and low mood while nocturnal bowel motions meant he was unable to sleep. He was compliant with his pancreatic enzyme replacement therapy during this period. Infective causes were ruled out by stool microbiology examination and coeliac disease by oesophagogastroscopy and biopsy. It was noticed that he was recently prescribed ramipril that was later stopped as a possible diarrhoea trigger. Diarrhoea started settling immediately and resolved to his baseline within a week. A colonoscopy was performed in the meantime and biopsies demonstrated microscopic colitis (MC). He did not tolerate budesonide well so was stopped. However, a follow-up colonoscopy with biopsy in two months showed resolution of MC.