Described herein is a system for controlling advance of a web material having characteristics of extensibility and comprising successive stretches of web for the production of respective articles, such as sanitary articles. In the passage from a delivery assembly to a treatment station functioning cyclically, the web material is subjected to extension. In order to ensure proper alignment of the individual articles with patterns or decorations provided thereon, the web must be fed to the treatment station in phase with the position reached by the treatment station within its operating cycle. A position sensor enables detection, for each stretch of web, of a real position of operation of the treatment station used for feeding the stretch of web itself to the treatment station with the aforesaid given phase relationship. A control module is able to detect the position error between the real position of operation and an ideal position of operation and to control the speed of operation of the delivery assembly to minimize the aforesaid position error. The system is configured for adaptively adjusting the aforesaid reference position so as to compensate for the variations of the characteristics of extensibility of the web material.