Abstract—Rice blast disease caused by Pyricularia oryzae Cavara is the most devastating rice diseases causing major yield losses worldwide. The presence of Pid3 gene, one of major blast resistant genes, was determined in 86 upland rice varieties from the northern region of Thailand using two deriver cleaved amplified polymorphic sequences (dCAPS) markers, Pid3-dCAPS 1 and Pid3-dCAPS 2. The PCR products were able to be classified into two alleles (resistant and susceptible alleles). Forty-four varieties showed the resistant Pid3 alleles of rice blast disease whereas 13 varieties revealed the susceptible alleles and 23 of them showed the heterozygous alleles. Nevertheless, these two markers could not distinguish between resistant and susceptible alleles in six varieties. The results from this study could be used in future development of rice blast disease resistance.