This paper reports the results of three field trials installed in the district of the Rio Paraíba Valley, a large potato producing area of the State of São Paulo, and they were carried out with a view of studying - in two of them - the behavior of six varieties of German origin, confronting two created by the Instituto Agronômico; the third one was intended for a competition among national varieties, in which was included, for comparison purposes, the "Delta A" variety, rather much cultivated in the area. From the results it became evident that varieties Aracy (IAC-2), Jacy (LAC-474), Piraquara (IAC-391) and Feldeslohn, were highly productive, with a marked tendency to produce large tubers. As for the leaf diseases, varieties IAC, with special reference variety Aracy (IAC-2), showed to be the most resistant to "Requeima", caused by Phytophthora infestans de Bary, and to "Pinta Preta", caused by Alternaria solani Kuhn.