The process took 6 months. I interviewed at World Health Organization (Washington, DC) in May 2011
Interview
You apply online through the website. It takes about 2 to 3 months to move to the next phase, that is a timed skills test. After the test it takes about 1 month to move to the next phase, which was a panel interview. After that you get an offer or not (it takes about 2 months to have a reply).