BACKGROUND: Between 2000 and 2010, Ireland became increasingly dependent on foreign-trained doctors to staff its health system. An inability to train and retain sufficient doctors to meet demand is the primary reason for the dependence on foreign-trained doctors. By 2008 the proportion of foreign-trained doctors was the second highest in the OECD. This increased dependence on international medical migration has both national and international policy implications. METHODS: Registration data were obtained from the Medical Council of Ireland (MCI) for a 10-year period: 2000-2010. Data indicate country of qualification but not nationality. The total number of registrants and entrants (n) was determined for each year. Immigration data were also obtained on the number of work visas issued to doctors. Registration and visa data were then compared in order to estimate doctor migration to Ireland 2000-2010. RESULTS: The proportion of foreign-trained doctors rose from 13.4% of all registered doctors in 2000 to 33.4% by 2010. The largest increase was in foreign-trained doctors from outside the EU, rising from 972 (7.4%) in 2000 to 4740 (25.3%) of registered doctors in 2010. The biggest source country in 2000 was Pakistan. By 2010, South Africa had become the biggest source country. The number of foreign-trained doctors from other EU countries doubled from 780 in 2000 to 1521 in 2010. CONCLUSIONS: Registration data are likely to over-estimate and visa data under-estimate the numbers of doctors actively working in Ireland. However, they serve to illustrate Ireland's rapidly increasing and potentially unsustainable reliance on foreign-trained doctors; and to highlight the need for better data to measure migratory flows. Improved measurement of health worker migration is necessary both for national workforce planning and to fulfil the requirements of the WHO Global Code on the International Recruitment of Health Personnel.