In the canton of Aargau (Northern Switzerland) an inventory of amphibian breeding sites, covering the whole territory, has been made in 1978/79. Altogether 918 waters were entered on a map, amongst them 94 brooks. The same inventory was repeated In 1991192 by much more collaborators who ascertained the amphibian stocks of 2267 waters, 919 of them being brooks. A comparison of the two inventories shows that in the time between 111 sites were destroyed and 141 spoilt, while 656 grounds remained unchanged and 331 new sites were created. The remaining sites could not be compared with each other for methodical reasons.