This publication examines the problem of tracing illicit small arms and light weapons in conflict settings. It identifies political factors as being the main obstacle to progress in limiting these arms, and stresses the need for international cooperation to enable the relevant authorities to trace sources, supply routes, and diversion points of illicit weapons, in a timely and reliable manner. The following topics regarding the limitation of small arms and light weapons are also covered in this publication: what to mark and what to trace, marking and record to keeping systems and modalities of operations, structures and institutions necessary to support the effective operation of a firearms tracing mechanism, and finally, small arms and light weapons traceability, a comparison of the principal existing international mechanisms.