This paper introduces G-LOTOS, a graphical language for the formal specification of concurrent systems. More precisely, G-LOTOS is a graphical syntax for the Formal Description Technique LOTOS, which is an ISO international standard. This paper requires no familiarity with LOTOS and can also be used as a first approach to the language. G-LOTOS is intended to provide a better readability and more intuitive understanding of formal specifications than textual LOTOS, and is itself being standardised in a joint ISO/CCITT effort. The introduction to the graphical syntax is supported by several short examples, by a complete G-LOTOS specification, and by a LOTOS/G-LOTOS conversion table.