In the years 2002-2008, missions were undertaken in the USA and Canada to search for wild and weedy Lactuca species. Altogether, 16 states in the USA (Arizona, California, Colorado, Idaho, Iowa, Minnesota, Montana, Nevada, New York, North Carolina, Oregon, South Dakota, Utah, Washington, Wisconsin and Wyoming) and two provinces in Canada (Ontario and Quebec) were visited. In total, seven wild and weedy Lactuca spp. (L. serriola, L. saligna, L. virosa, L. canadensis, L. biennis, L. floridana, and L. ludoviciana), an interspecific hybrid (L. canadensis x L. ludoviciana), and an undetermined Lactuca species were observed and collected in 200 locations. In this paper, we present new data on the distribution and ecobiology of Lactuca naturally occurring in North America. Morphological assessment of L. serriola samples acquired from North America revealed considerable intraspecific phenotypic variation. Although L. serriola samples originating from various eco-geographical regions differed significantly in their genetic polymorphisms (based on AFLP markers), little variation was observed in their absolute DNA content.