Review Questions/Objectives The objective of the systematic review is to synthesize the best available research evidence on the epidemiological association between non-melanoma skin cancer NMSC (and its subtypes) and smoking, alcohol and BMI. Inclusion Criteria Types of Participants We will include adults (18+ years old) of either gender from any ethnicity. Patients with genetic syndrome, for example Gorlin Syndrome, Xeroderma Pigmentosa, albinism; or any other condition that increases the risk of developing a BCC/SCC; patients with recurrent tumours and patients taking immunosuppressants (for example, transplant patients) will be excluded. The phenomena of interest The focus of interest for this systematic review is the epidemiological association between exposure to modifiable lifestyle factors such as smoking, alcohol consumption and body mass index (BMI) and non-melanoma skin cancer NMSC (and its subtypes). Types of Exposures Smoking measured either using self-reported status or consumption, or using biochemical markers (for example cotinine) will be eligible. We will include all forms of tobacco exposure, including cigarettes, cigars, chewing tobacco and roll-ups. Self-reported smoking status that was verified by either carbon monoxide measurements will be used in preference to sole self-reported status included. Body mass index (BMI) measured either using self-reported status or through measured BMI, derived from height and weight measurements, will be included. We will additionally include other anthropometric measurements including waist to hip ratio and the percentage body fat. Alcohol consumption measures either using self-reported status or consumption using a measureable quantity of alcohol, such as drinks per week or units of alcohol, will be included. Types of Outcomes We will assess the effect of the above exposures on: i) The risk of squamous cell carcinoma ii) The risk of basal cell carcinoma iii) The risk of non-melanoma skin cancer We will include any eligible lesion location anywhere on the skins surface, excluding the lip. Additionally, we will exclude internal head and neck cancers.