In four field experiments the peanut cultivars Florigiant and NC 7 were generally more susceptible (P = 0.05) than Pronto and Spanco to pod rot and sometimes more susceptible (P = 0.05) than Florunner, GK 7, Langley or Okrun. The pod rot susceptibility of Florunner, GK 7, Langley, Okrun, Pronto and Spanco was usually similar. No consistent cultivar differences (P = 0.05) among pod yields were observed. Pythium myriotylum was the dominant species isolated from infected hull pieces plated on a medium selective for pythiaceous fungi. No cultivar significantly reduced populations of Pythium spp. in the soils of their pegging zones. In 1987, populations of Pythium spp. in soils at Ft. Cobb and Madill, Oklahoma increased at 67 days after planting (DAP) but declined at 89 DAP. in 1988 a similar population trend occurred at Ft. Cobb at 89 DAP and at Enos, Oklahoma at 127 DAP. The increase and decline of Pythium spp. were probably not directly influenced by soil temperature or matric potential. The involvement of the peanut plant in the fluctuation of Pythium spp. in soil is a plausible explanation for this trend.