Since 1986, the Shoklo Malaria Research Unit (SMRU) has provided basic healthcare and carried out research aimed at reducing the impact of multi-drug resistant malaria and other infectious diseases in the area on the border between Thailand and Myanmar. SMRU's main area of interest is in malaria, with special interest in children and pregnant women - the groups most at risk from malaria - and it has combined this research with the operation of antenatal clinics along the border. SMRU currently runs multiple free clinics for the Karen and Burman border population that would otherwise lack access to health care. The most distant clinic is about 120 km from the SMRU office in Mae Sot. Carrying out research and providing care along the border presents a range of unique practical and ethical challenges. This in part because the people who live near the border are mostly migrants or refugees from elsewhere in Myanmar who have, since the 1980s, moved to the border area to escape economic hardship and sometimes conflict and persecution. There are currently thought to be two million migrants from Myanmar living in Thailand (about 150 000 in refugee camps) and a further million 'internally displaced' people living near the border inside Myanmar, although numbers are difficult to verify. The vast majority of these people, who come from a very diverse range of different ethnic, religious, political and language groups, live in insecure, unsafe conditions and face a number of serious health difficulties.