Phymatotrichum root rot is a fungal disease with a host range that includes many economically important crops in the southwestern United States and Mexico. While it has been studied since the late nineteenth century, ecological relationships of the disease, particularly those related to its distribution and dispersal, are not understood. Combined ground radiance sampling and aerial photographic interpretation was employed to study the distribution of Phymatotrichum root rot in cotton. Radiometric ground sampling showed that diseased cotton has a characteristic spectral signature that is significantly different from healthy cotton at visible wavelengths. Micro-scale examination of distribution within fields utilized multitemporal photography, both within season (1983) and for four seasons (1979-1982), revealed that the disease spreads during a season, but is not recurrent in many cases between years. Meso-scale mapping employed multitemporal photography to map distribution during a four-year period. When compared to mapped soil units, these data revealed a significantly non-random relationship between the diseased areas of fields and fine-textured soil units that may be based on moisture-holding potential. A yield analysis was also preformed using Thematic Mapper Simulator data and computer analysis.