SummaryThis research was the first cytogenetic study of the lesser bamboo rat (Cannomys badius) from Nongbualamphu, Nongkhai, Loei and Udonthani Provinces, Thailand. Blood samples were taken from 8 males and 6 females and then subjected to standard whole blood T-lymphocyte culture. The samples were harvested by colchicine-hypotonic-fixation-air-drying technique and followed by conventional, GTG-, CBG-, Ag-NOR banding and high-resolution techniques. The results showed that the diploid number was 2n=50 and the fundamental number (NF) was 94 in both males and females. The autosomes consist of 12 large acrocentric, 2 medium submetacentric, 10 medium acrocentric, 4 small metacentric, 6 small submetacentric, 8 small acrocentric and 6 small telocentric chromosomes. X chromosome was the largest submetacentric chromosome, while the Y chromosome was small acrocentric chromosome. From GTG-banding and high-resolution techniques, the numbers of bands and locations in the C. badius were 262 and 302, respectively, each chromosome pair could be clearly differentiated. CBG-banding shown C-positive (dark band) on the centromere of all autosomes. However, C-negative (light band) shown on Y chromosome. From Ag-NOR banding, there is no detection of nucleolar organizer regions. All of these results can advantage as the useful basic genetic information for C. badius cytogenetic study. The karyotype formula for C. badius could be deduced as: L The subfamily Rhizomyinae of rodents includes the Asian bamboo rats. The subfamily is grouped with the Spalacinae and the Myospalacinae into a family of fossorial muroid rodents basal to the other Muroidae. The group includes 17 species classified in 3 genera (Rhizomys, Cannomys, Tachyoryctes) and 2 tribes (Rhizomyina, Tachyoryctini). The tribe Rhizomyini includes 4 species namely; Hoary bamboo rat (R. pruinosus), Chinese bamboo rat (R. sinensis), large bamboo rat (R. sumatrensis), and lesser bamboo rat (C. badius) (Lekagul and McNeely 1988, Wilson and Cole 2000, Parr 2003, Musser and Carleton 2005.The C. badius a small, fairly stocky rodent, whose smaller size distinguishes it from other bamboo rat species. It is covered with soft, dense, chestnut brown fur over the entire body, head and limbs. Some individuals show a vertical white streak of fur the snout up over the forehead. The cheeks are slightly paler brown. The comparatively short tail is virtually naked, covered in hairs.