Over 150 days were spent sampling the Eastern National Water Carrier during the period June 1985—August 1986. 3445 vertebrates of over 100 species were removed, of which over 55% were snakes and 10% tortoises. Five species of frog have also been recorded from the EWC. Of most concern is the bullfrog, Pyxicephalus adspersus, of which 1500 were found in the canal during December 1915—February 1916. Only two lizards, Acontias percivalli and Varanus exanthematicus, of 35 species recorded from the vicinity, regularly enter the canal but neither are cause for concern. Nearly 3000 snakes have been removed, and because of predation and sampling factors, this is believed to represent only 30% of the total entering the canal. The commonest species include four Psammophis spp. (21%) Atractaspis duerdeni (20%), Bitis caudalis (12%) and Aspidelops scutatus (11%). The development of remedial measures to prevent this problem is being addressed.