While the number of medical-school campuses in Arizona doubled--from two to four--in the last few years, there is no assurance that all of the new doctors they graduate will stick around to practice in the state. Medical schools here and nationwide are struggling to line up enough clinical-training slots so that an influx of new upper-level medical students will have somewhere to practice their skills. In many ways, the Phoenix area is a microcosm of what is happening nationally. Faced with the prospect that aging baby boomers may not have enough doctors to care for them, medical schools are expanding class sizes and opening new campuses. But the pipeline could remain clogged if they aren't able to find enough training sites.