The cut ends of 15-cm-long shoot tips from 15 peanut genotypes were immersed individually in 1 × 14 cm test tubes containing Hoagland's solution. Shoots were supported by foam plugs leaving about 12 cm extending above the foam plugs. All leaves were removed leaving about 1 cm of each petiole on the shoot. A 4-mm-mycelial plug of Sclerotinia minor, taken from the periphery of a 2-day old culture grown on potato dextrose agar containing 100 ug/ml streptomycin sulfate (SPDA), was placed between the stem and a petiole in the middle of the shoot. Tubes with shoots were then placed in a polyethylene enclosure on a greenhouse bench where the day and night temperature were 29 ± 2C and 25 ± 2C, respectively. Relative humidity (RH) was maintained at 95 to 100% by lining the bottom of the enclosure with wet burlap. Lesions appeared on shoot tips 3 days after inoculation, and their length was measured at various times. Genotypes with the least percent of symptomatic stems also had the lowest rates of lesion expansion. Two weeks after inoculation, tubes were drained, and shoots remained in the chamber at about 60–70% RH to allow sclerotial production. Sclerotia from each shoot were removed, counted, and their viability determined by germination on SPDA at 25 ± 2C in darkness. This method was effective in differentiating the reaction of peanut genotypes to infection by S. minor.