The labeling of glass is an important processing step for the pharmaceutical industry that allows tracing and controlling of their products. The current techniques, i.e. color bar codes or labels, have several disadvantages, e.g. lack of permanency and susceptibility for tampering, limited adhesion and problems during sterilization. Direct laser engraving on the surface is a very flexible method that allows permanent marking of vials with 2D data matrix codes. The feasibility of this technique for an industrial environment was proven by determining the influence of key parameters such as laser fluence, pulse number and laser wavelength. The visual appearance of the data matrix can be controlled by varying the pulse number, laser fluence and marking precision. (C) 2003 Elsevier B.V. All rights reserved.