Ten species of Trillium (Liliaceae) are known to occur in Virginia. Taxonomic key, morphological descriptions, distribution maps and chromosome numbers are presented. A chromosome number of 2n = 10 was verified for: Trillium cernuum, T. erectum, T. flexipes, T. grandiflorum, T. luteum, T. nivale, T. pusillum, T. sessile, T. sulcatum, and T. undulatum. Some chromosome morphology data are applied to the discussion of T. pusillum, and also reinforce that T. sulcatum and T. erectum are separate taxa.