Abstract: Sheath blight of rice caused by Rhizoctonia solani Kuhn (Teleomorph: Thanatephorus cucumeris (Frank) Donk) is gaining devastating potential in India. The pathogen is reported to show variation in expression of symptoms on the genotypes grown in different locations. Twenty isolates from different districts of Karnataka were collected to examine the cultural and morphological variability. In the PDA culture, the isolates displayed a significant variation in colony characteristics, ranging from compact sparse to compact dense mycelial development and from white to brown in color. Variations in sclerotial production, distribution, abundance, and color were also noted, resulting in colonies that ranged in color from light brown to dark brown, along with central to scattered distribution, rough to smooth sclerotia. R. solani isolates from other districts may also have their biology examined using the same cultural and morphological criteria as were employed in this study.