Technical Abstract: A seedling assay was developed for Verticillium wilt (VW) resistance in potato (Solanum tuberosum) in order to provide efficient and rapid screening to identify resistant clones in segregating populations. The method provides uniform inoculum to avoid false negatives and reduces the confusion of symptom expression with late maturity in field grown plants. Seedlings of 18 potato families were tested. Although symptom expression of seedlings, such as severe stunting, chlorosis, and necrosis was obvious, the relationships between seedling score and either symptom expression or stem colonization in the field were not apparent. When exudates were separated from fungal mycelia grown in liquid culture and inoculated in 5 families and S. chacoense population, each family reacted differently from each of toxin or Verticilium dahliae conidia inoculum. This result suggests that phytotoxins that may be present can cause serious effects on the growth of certain genotypes. Seedlings were also selected based on no symptoms and low V. dahliae biomass after infection. All selected clones showed lower V. dahliae biomass than susceptible control plants. The results indicate that the seedling assay can be effectively used to identify resistant or tolerant clones in segregating populations.