The purpose of this study was to examine the effect of immigrant status and years lived in the United States on the general health status of California's foreign-born populations. Two models were constructed using California's aggregate adult population and the adult foreign-born population. A binary logistic regression was conducted using data from the 2003 California Health Interview Survey. California's immigrant populations were found to enjoy a self-assessed health advantage compared to California's US-born population. The results present evidence of a downward trend in self-assessed health amongst California's foreign-born population associated with increased years lived in country. The initial health advantage found among California's foreign-born appears to function mainly through socio-economic factors. These results suggest that the deterioration in health associated with increased years lived in the US may be an effect of immigrants' exposure to California's environmental determinants of human health rather that the loss of culture-specific protective factors.