The present study aimed to chemically characterize 31 accessions and seven cultivars of basil. The percentage composition of the essential oils of the accessions and cultivars was based on the 14 most abundant constituents: 1,8-cineole, linalool, methyl chavicol, neral, nerol, geraniol, geranial, methyl cinnamate, β-bourbonene, methyl eugenol, α-trans-bergamotene, germacrene-D, epi-α-cadinol, and δ-cadinene. The genetic materials were classified into eight clusters according to the chemical composition of the essential oils: Cluster 1--mostly linalool and 1,8-cineole; Cluster 2--mostly linalool, geraniol, and α-trans-bergamotene; Cluster 3--mostly linalool, methyl chavicol, methyl cinnamate, and β-bourbonene; Cluster 4--mostly linalool, methyl chavicol, epi-α-cadinol, and α-trans-bergamotene; Cluster 5--mainly linalool, methyl eugenol, α-trans-bergamotene, and epi-α-cadinol; Cluster 6--mainly linalool, geraniol, and epi-α-cadinol; Cluster 7--mostly linalool and methyl chavicol; Cluster 8--mainly geranial and neral.