Blue mold has occurred each year on North Carolina's Burley tobacco crop since the major epidemic of 1979. We began collecting and monitoring Peronospora tabacina isolates from North Carolina in the mid- 1980's, and have tested their sensitivity to metalaxyl (Ridomil) using a tobacco seedling assay procedure. Prior to 1991, all isolates in our tests at Fletcher, NC were metalaxyl sensitive (ms) at 0.1 µg ml^-1. However, in 1991 a small percentage (< 10%) of P. tabacina isolates were metalaxyl insensitive or resistant (mr) at 100 µg ml^-1. Between 1991 and 1995, P. tabacina populations contained a mixture of ms and mr isolates and between 1996 and 1999, only mr isolates were detected in North Carolina. We began monitoring sensitivity of P. tabacina isolates to dimethomorph (Acrobat) in 1995 using a floating leaf-disc assay procedure. All isolates collected in 1995 and since have been sensitive to dimethomorph at 1.0 µg ml^-1. These studies provide a historical record of population shifts in metalaxyl sensitivity and show current stability in dimethomorph sensitivity in the blue mold pathogen population monitored in North Carolina.