I found this in the Guardian on the train on the way home, and thought I had missed it in the BMJ that I read earlier - but it turns out to be in a supplement.
This is a list of the 15 most important medical discoveries made since the foundation of the BMJ in 1840. This is the list of 15, shortlisted from a list of 100:
Chlorpromazine - a drug to treat schizophrenia
Evidence based medicine
Magic bullets - monoclonal antibodies
The (contraceptive) pill
Risks of smoking - recognition of
It is interesting, in closing, that some of these are still goals, rather than milestones, in some parts of the world.
Later note: I reworded this entry this morning (9th January). It appears in Libworm, and Libworm only gives the first few words of the original entry, and this gives a false impression of what I was saying.
Another later note: sanitation "won", with antibiotics and anaesthesia close behind. See http://www.bmj.com/cgi/content/short/334/7585/111-a?etoc