A total of about 850 PCP-treated southern pine poles from four supplier/year combinations were inspected by a contractor. Their core samples were cultured to isolate wood-rotting basidiomycetes and thin sections were examined under the microscope. The incidence of decay based on inspections and basidiomycete isolates, excluding S. brinkmanii, was 4% for TDL-85s, 3% for TDL-86s and 1% for TD4-85s. Microscopic examination revealed comparatively little damage in the groundline region. This was consistent with the lower frequency of isolation of basidiomycetes at the groundline compared to the Bell attachment position. It was also consistent with the distribution of decay and extensive end-grain penetration of preservative found in the intensive examination of selected poles. Conclusive evidence for pretreatment infection as the origin of the decay problem came from the pattern of dacay found in the intensive examination. This origin would also explain the distribution of fungi in the poles in service and the failure of some poles, due to decay, within five years of installation. At least 3% TDL-85s could continue to lose strength unless there is sufficient preservative retention and penetration to prevent this.