This document is aimed at a technical audience and reports on the scientific information which underpins the hazard assessment of a specific substance. Studies show that respirable crystalline silica (RCS) has the potential to cause lung cancer in humans, especially when that exposure is heavy and prolonged. This document aims to address a number of questions relating to the carcinogenic potential of RCS. It contains conclusions on key issues relating to RCS, appraisal of key epidemiological studies carried out across the world, and relevant experimental and animal data. Contents: Summary; Background; Section 1: Conclusions on key issues; Section 2: Individual appraisal of key epidemiological studies; Section 3: Experimental and animal data; References.