A total of five insects have been introduced into California for control of yellow starthistle. Three of these insects have been distributed statewide through a series of workshops and training programs. In 2000 and 2001, a survey of 422 locations sampled yellow starthistle in all regions where yellow starthistle occurs in California and the plant samples examined for the presence of the three biological control insects. The results show that the weevil, Eustenopus villosus, is the most widespread insect occurring in over 80% of the locations. The weevil, Bangasternus orientalis, was second, occurring in over 70% of the sample locations and the gall fly, Urophora sirunaseva, was third, occurring in over 60% of the sample locations. Also, the results show that the seedhead fly, Chaetorellia succinea, a tephritid fly accidentally introduced into southwestern Oregon in 1991, was the most widespread insect, occurring in 99% of the sample locations. Spread of this insect was due to its own efforts and not from the redistribution efforts. Projecting the location and abundance information on a map using GIS showed regional differences in abundance among the biological control insect. The differences will be discussed.