Technical Abstract: In the present study compound Inter-Simple Sequence Repeat (ISSR) primers containing CA/GT-repeat motifs in their sequences were utilized to estimate the population genetic structure of Homalodisca coagulata (Say). Eighteen populations from throughout the U.S. and a population from Tahiti, French Polynesia were analyzed. The 18 U.S. populations were arbitrarily assigned to three regions: southeastern, southwestern (Texas), and western (California) regions. A total of 62 and 91 neutral polymorphic markers were identified with p-15 and p-13, respectively. Exact tests for population differentiation indicated significant differences in marker frequencies among the 18 populations with both primers; in addition, significant differences were also observed within each region. Analyses of molecular variance (AMOVA) showed a significant partitioning of gene diversity among regions, 11% with p-15 and a lower value of 3% with p-13. The majority of the variance, however, were distributed within populations, 83 and 88% with p-15 and p-13, respectively. Comparison of other genetic differentiation estimates showed values for GST (8-11%) and ' (7-10%) for among regional variation that were of comparable magnitudes to the AMOVA results. A dendrogram based on Reynolds coancestry distance performed with p-15 clustered the U. S. populations into two main groups. The southeastern populations were grouped into one cluster and the southwestern and western populations into a second cluster. Within the western region, dendrograms produced with p-13 and p-15 showed in both cases that the Edison and Bakersfield populations clustered as outliers. The present results estimate, for the first time, the population genetic structure of H. coagulata and suggest that a subset of insects in California may have their origins in the southwestern region (Texas); furthermore, these results are suggestive of more than one founding event in California.