OBJECTIVE: The fungus Rhizoctonia solani is an important seedling pathogen to many plant hosts including cotton (Gossypium). For multiple annual crops there have been relatively few screenings of germplasm conducted to identify potential sources of resistance to R. solani, and for cotton we have not been able to identify any recent germplasm screenings for resistance to this seedling pathogen. Therefore, the objective of this study was to screen historical as well as more recently developed Upland (Gossypium hirsutum L.) and Pima (Gossypium barbadense L.) cotton germplasm for resistance/susceptibility to R. solani. RESULTS: The results of the R. solani screening found no significant differences among 85 Upland and 10 Pima cotton genotypes, which were all similarly susceptible to R. solani based on data for root rot and fresh root weight. While Upland and Pima cotton make up the majority of cotton grown worldwide, the lack of resistance identified in both historical and newer Upland and Pima germplasm suggests a pressing need for further exploration and selection of novel sources of resistance within the vast genetic diversity of different domesticated and wild cotton species.