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Rice is the major food crop in India. It is affected by many fungal, bacterial and viral diseases. Among them, brown leaf spot caused by Bipolaris oryzae is one of the important disease which reduces the yield (6-90%) and quality of the crop. The present investigation was carried out to study the cultural and morphological characteristics of Rice brown spot in Cauvery command region of Karnataka. Roving survey was conducted in Hassan, Mandya, Mysuru and Chamarajanagar districts of Cauvery command region to record the disease severity of brown leaf spot of rice during kharif 2022 and disease severity was expressed in Percent Disease Index (PDI). The symptoms are seen on coleoptile, leaves, panicle branches, glumes and spikelet and in the field it is recognized by the greyish brown spots. Among the four districts surveyed, the mean PDI was highest in Mysore (12.11 %) and least was recorded in Chamarajanagar district (7.21 %). Among the different media's tested, paddy leaf extract agar showed maximum radial growth (80.40 mm) in all the isolates followed by potato dextrose agar (78.80 mm). Different isolates showed different colony characters, colony diameter, colony abundance, colony colour, margin, texture, topography and time taken to cover entire petri plate. Conidia in different isolates were light brown, brown and dark brown with size ranging 16.39 - 103.06 × 6.45 - 19.60 µm. The shape of the conidia was either curved, slightly curved, spindle or fusoid and number of septa was between 3-10. [ABSTRACT FROM AUTHOR]