Abstract Evidence is presented for the occurrence of two races of Pseudomonas pisi. Seven isolates from New Zealand and overseas, pathogenic to cv. Early Onward but non-pathogenic to cv. Partridge, were designated race 1. Similarly 16 isolates, pathogenic to cv. Partridge but non-pathogenic to cv. Early Onward, were designated race 2. Tests on eight pea cultivars showed that two were resistant to race 1 but not race 2, three were susceptible to both races, and three were susceptible to race 1 but resistant to race 2. In a search for resistance in other cultivars and wild-type peas two lines, 3080 and cv. Vinco, were apparently resistant to both races under glasshouse conditions. The significance of race 2 to the present disease problem in New Zealand is discussed.