A range of environmental and host factors has been identified to explain the etiopathogenesis of squamous cell carcinoma of the lip. However, the definitive pathogenic pathway remains unclear. Carcinogenesis does not seem to be limited to a single agent, but rather to a complex multistep process of interactions between putative risk factors. In this paper, the currently available data regarding risk factors, considered to be causally related to the onset of lip cancer, are reviewed.