Research on biological control of weeds in the United States began early in this century with the use of introduced insects to control the weed, lantana (Lantana camara L.), in Hawaii. The highly successful program for biological control of St. Johnswort (sometimes called “Klamath weed”) (Hypericum perforatum L.) in California by the use of introduced insects in the 1940's and 1950's caused increased interest in this approach to weed control. As a result of this increased interest, the United States Department of Agriculture (USDA) established two overseas laboratories to study arthropod natural enemies of a number of weeds that had been introduced into the United States – in Rome, Italy, in 1959; and near Buenos Aires, Argentina, in 1962. The recent and successful use of an introduced rust pathogen (Puccinia chondrillina Bubak & Syd.) to control rush skeletonweed (Chondrilla juncea L.) in Australia, and the production and utilization of pathogens for control of weeds in the United States, has spurred further interest in biological control.