Abstract: Eifteen hybridoma cell lines secreting monoclonal antibodies (McAbs) against Xanthomonas campestris pv. oryzicola were established. The chromosome numbers of the hybridoma cell lines ranged from 98 to 104. The ELISA titers of the culture supernatants and the ascitic fluid were 102—103 and 105—106, respectively. Seven of the fifteen McAbs belonged to IgG3, three to IgG2a, one to IgG2b and four to IgM. The reaction of the mcAbs with X. c. pv. oryzicola was specific and none of the McAbs reacted with other patnogenic varieties in X. campestris, such as X. c. pv. oryzae, strains of other 4 plant pathogenic bacterial genera and some becteria on the surface of rice leaves and seeds.