Objective . To estimate the prevalence of alarm symptoms for breast, colorectal, urinary tract, and lung cancer in the general population. Design. Cross-sectional questionnaire survey. Setting. The former County of Funen, Denmark, with 480 000 inhabitants. Participants . A total of 13 777 randomly selected persons aged 20 years and older. Main outcome measures . Prevalence estimates of having experienced cancer alarm symptoms during the past 12 months: a lump in the breast, blood in bowel movements, blood in urine, or coughing for more than six weeks. The number of alarm symptoms experienced within the past 12 months was also calculated. Results . With a response rate of 69%, 3.3% of responders (95% CI 2.9% to 3.7%) reported a lump in their breast, 5.7% (5.2% to 6.3%) reported blood in bowel movements, 2.2% (1.9% to 2.5%) reported blood in urine, and 6.5% (6.1% to 7.5%) reported coughing for more than six weeks within the past 12 months. Overall, 15.3% (95% confi dence interval 14.3% to 16.3%) of the females and 12.7% (11.6% to 13.7%) of the males reported having experienced at least one cancer alarm symptom within the past 12 months. Conclusion . Alarm symptoms of breast, colorectal, urinary tract, and lung cancer are common in the general population and approximately 15% of the population have experienced at least one of these cancer alarm symptom within the past 12 months.Key Words: Breast cancer , colorectal cancer , cross-sectional survey , health surveys , lung cancer , signs and symptoms , urinary tract cancer In order to reduce cancer mortality and morbidity, health care systems have primarily focused on prevention and treatment strategies [1,2]. However, in recent years focus has also been on reducing the time span from when a person experiences a symptom that could potentially be caused by cancer, until the diagnosis has been made [3,4]. One approach has been that patients presenting with cancer alarm symptoms should promptly be referred for clinical investigations [1,2] and many campaigns aim to encourage people to contact their general practitioner immediately when experiencing alarm symptoms [5]. Furthermore, in many countries alarm symptoms give access to the fast track cancer diagnostic pathways [1]. Studies have been made with general practice patients [6]. It is the general practitioner who decides which patients warrant referral, but little is known about the prevalence of cancer alarm symptoms in the population.If alarm symptoms are frequent in the general population, the positive predictive values for cancer alarm symptoms would be low and many healthy people might become unduly worried about having cancer and be investigated for cancer [7]. Hence, prevalence estimates of cancer alarm symptoms are important. Can we actually base our referral guidelines on alarm symptoms of cancer? For most general practitioners the prevalence of alarm symptoms of cancer will be tacit knowledge. We therefore aimed to determine the prevalence of cancer alarm symptoms of common cancers in the general ...