Basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) are clinically and pathologically distinct and both are locally invasive. However, while BCCs rarely metastasise, SCCs have the potential to do so especially when they arise on the ears or lips. UV radiation is the most important risk factor for non-melanoma skin cancer (NMSC). The tumours most commonly arise in fair-skinned individuals on sun-damaged skin, especially the face. Incidence rises with age. Patients with one NMSC have a higher risk of developing another NMSC and of malignant melanoma. SCCs are frequently more difficult to diagnose than BCCs. Well differentiated lesions have a pronounced keratotic element. Poorly differentiated SCCs tend to be pink or red papules or nodules, lacking keratin, which may ulcerate. Around 5% of SCCs metastasise. High-risk SCCs include those: on the ear, lip, or sites unexposed to the sun and in chronic ulcers, scars or Bowen's disease. SCCs > 20 mm in diameter or > 4 mm in depth are high risk. Patients who are immunosuppressed, have poorly differentiated tumours or recurrent disease are also at increased risk. Patients with a slowly evolving or persistent skin lesion where cancer is a possibility should be referred to a dermatologist. Lesions suspected of being BCC should be referred routinely. Urgent referral should be reserved for cases where there is concern that a delay may have a significant impact because of the size or site of the lesion. Any non-healing lesions >1 cm with marked induration on palpation, showing significant expansion over eight weeks, should be referred urgently as they may be SCCs.