Gammarus tigrinus was introduced in the Netherlands around 1964. Previous papers recorded the spreading of this amphipod in the successive years. In the period 1968-1970, it has invaded new regions in the provinces of Friesland, Groningen, Overijssel, Gelderland, Noord – Holland and Zuid – Holland, as well as in the Noordoostpolder and Oostelijk Flevoland. The maximum progress made since 1967 is about 36 kilometers. It is recorded for the first time south of the river Rhine.