Abstract: SINCE 1941, I have been testing South American tuber-forming Solanum species for immunity and resistance to the potato-root eelworm. The material, kindly supplied by Dr. P. S. Hudson and Dr. J. G. Hawkes, of the Commonwealth Bureau of Plant Breeding and Genetics, Cambridge, forms part of the Commonwealth Potato Collection1. An interim report on this work was published in 19452, when about fifty forms had been examined. Since then, however, owing to a grant from the Commonwealth Agricultural Bureaux, it has been possible to increase the scale of the tests, and about seven hundred forms have now been examined.