The current wave of immigration to the United States--mostly Asians and Latin Americans--may well be the largest in the 20th century. Many newcomers practice habits of health and hygiene deficient by American standards. Some prefer the shaman to the physician and traditional herb remedies to modern medical therapies. Physicians find themselves practicing at an invisible border separating them from their foreign-born patients, where differences of language and culture can lead to misunderstanding and frustration, impeding a physician's ability to gain cooperation with prescribed therapy. Similar issues faced physicians at the turn of the century. Newly arrived Italians, East European Jews, and Chinese were often ambivalent toward physicians and their therapies. Quacks further undermined the physician's credibility among immigrants. Today, some physicians try collaborating with shamans and herbalists to accommodate patients' cultural preferences. Respect for the customs and taboos of immigrant patients pays dividends in physician effectiveness and efficiency.