Studies show higher house dust and body burden levels of PBDE flame retardants in North America than Europe; but little is known about exposure variation within North America, where California's furniture flammability standard affects PBDE use. We compared dust samples from 49 homes in two California communities with 120 Massachusetts homes and with other published studies. Dust concentrations [median (range) ng/g] in California homes of BDE-47, -99, and -100 were 2700 (112-107,000), 3800 (102-170,000), and 684 (<MRL-30,900), respectively, and were 4-10 times higher than previously reported in North America. Maximum concentrations were the highest ever reported in indoor dust. We then investigated whether human serum PBDE levels were also higher in California compared to other North American regions by analyzing the 2003-2004 National Health and Nutrition Examination Survey (NHANES), the only data set available with serum from a representative sample of the U.S. population (n=2040). California residence was significantly associated with nearly 2-fold higher sigma PBDE serum levels [least square geometric mean (LSGM) ng/g lipid, 73.0 vs 38.5 (p = 0.002)]. Elevated PBDE exposures in California may result from the state's furniture flammability standards; our results suggest the need for further research in a larger representative sample.