The highest total number seems to be from China - i have seen a figure of 30 tests quoted, but can't find the source so it shouldn't be taken as accurate. This high figure is partly explained by the simple fact that China has by far the world's highest population and sends a proportionately high number of athletes. Another reason is that in the 1980s and 1990s the Chinese state actually allowed the use of performance enhancing drugs, which has pushed up the figures. Most of the cases that have been detected involve swimming. However, in the most recent story involving a Chinese swimmer, Gold medallist Ye Shiwen, while accusations were made there is actually no reason to think she was doping at all, and she has passed all the tests.

Olympic doping has a very long history - even in ancient Greece, athletes ate special foods to try and enhance their performances, including lizard meat prepared in a way that was supposed to boost their energy levels.