Introduction: The objective of this study was to investigate the evidence for positive predictive value (PPV) of alarm symptoms and combinations of symptoms for colorectal cancer, breast cancer, prostate cancer and lung cancer in general practice. Methods: This study is based on a literature search performed in PubMed, Embase, the Cochrane database and at ClinicalTrials.gov in accordance with the PRISMA guidelines. The main outcome measure used was PPV. Results: A total of 16 eligible studies were identified. The intervals in the brackets refer to the variation of the results in the studies. Colorectal cancer: The PPV of “rectal bleeding” was high for patients > 60 years (6.6-21.2%), but much lower in younger age groups. For “change in bowel habits” and “significant general symptoms”, the PPV was 3.5-8.5%. Breast cancer: “Palpable suspected tumour” was well supported (8.1-24%). No studies on the predictive value of “pitting of the skin”, “papil-areola eczema/ulceration” and “suspect axillary lymph nodes” were found. Prostate cancer: One study showed a high PPV for positive rectal examin­ation (12%). The value for “lower urinary tract symptoms” was low (1.0-3.0%). PPV for “perianal pain” and “haemospermia” were not found. Lung cancer: For “haemoptysis” the PPV increased from 8.4 in patients aged 55 years to 20.4 at the age of > 85 years. PPV for “cough”, “pain in the thorax”, “dyspnoea” and “general symptoms” were low (0.4-1.1%). Using a new algorithm that estimates the PPV of combinations of symptoms and risk factors, a higher PPV may be achieved. Conclusion: A few of the alarm symptoms show a high PPV, whereas the PPV for some symptoms currently remains unknown. To improve the GPs’ diagnostic judgment, a new algorithm for calculating the PPV for combinations of symptoms and risk factors seems promising.