Lantana is a major weed throughout eastern Australia and the South Pacific. Lantana is a major weed of grazing, forestry, plantation and conservation areas east of the Great Divide in Australia and in many South Pacific Islands. Effective control can be achieved by a combination of slashing, burning, and herbicide application, but this may not be economical or practical particularly in inaccessible sites. L.commara, the principal pest species, occurs as a complex of varieties that varies in susceptibility to both chemical and biological control. The available morphological basis for identification of varieties is inadequate. A genetic investigation examining relationships within and among Australian and South Pacific taxa is proposed as a basis for identifying the weedy varieties. This investigation will underpin later work on formulation of recommendations for management of L.camara based on varietal differences in susceptibility.