Following the First Colloquium held at Verona in 1969, it was planned to hold at Lyon in July, 1973, the Second International Colloquium dealing with the genus Niphargus and also with the genus Gammarus. As subject matter in discussions dealing with the first of these genera, the meeting was devoted mainly the balancing the various viewpoints (based on the European approach) and initiating a collective study of the systematics of these hypogean Amphipoda. The systematics are currently quite confused. Several modifications of the propositions of the Colloquium at Verona (published in 1972) were discussed. A third Colloquium, with the same objectives, is planned after an interval of three years.