Cystic fibrosis (CF) is the most common fatal inherited disease in Caucasian people. Recent data indicate that there are more than 9,000 patients with CF in the UK. This would equate to around one or two patients for an average GP practice. Recognising the symptoms and signs that may point to a diagnosis of CF is important so that appropriate referral and investigations can be organised. Symptoms suggestive of CF in the first two years of life include failure to thrive, steatorrhoea, recurrent chest infections, meconium ileus, rectal prolapse and prolonged neonatal jaundice. In older children, additional suggestive symptoms include ‘asthma'-like symptoms, clubbing and idiopathic bronchiectasis, nasal polyps and sinusitis, and heat exhaustion with hyponatraemia. Suggestive symptoms in patients who present in adulthood, who are more likely to have atypical CF, include azoospermia, bronchiectasis, chronic sinusitis, acute or chronic pancreatitis, allergic bronchopulmonary aspergillosis, focal biliary cirrhosis, abnormal glucose tolerance, portal hypertension and cholestasis/gallstones. [With external links to the evidence base]