In this article the authors report about the results of field trials, carried out in the districts of Socorro, Tatuí and Porangaba, in the State of São Paulo, with a view to study the behaviour of national (IAC) varieties of potato (Solatium tuberosumL.). According to results obtained, varieties Aracy (IAC-2), Itaiquara (IAC-3551) and Jacy (IAC-474) showed to be highly productive, whereas varieties IAC-4183, Irai (IAC-S67) and also Aracy (IAC-2) presented high percentages of Special type tubers. With regard to leaf diseases, Aracy (IAC-2) stood out among the others due to the marked resistance shown to «Requeima da batatinha» which is caused by the fungus "Phytophthora infestans"(Mont) de Bary, as well as to nematodes which produce «galhas» in the tubers.