The development of sanitation has been the greatest medical advance in the last 166 years, according to a vote of more than 11,000 people worldwide.
The construction of a London sewer in 1859
Sanitation received 15.8% of the votes, beating other advances including the discovery of antibiotics and the development of vaccines.
Inadequate sanitation remains a problem in the developing world, contributing to millions of deaths.
The contest was run by the British Medical Journal.
Leading doctors and scientists were chosen to champion each of the breakthroughs and included Professor Carl Djerassi, who created the Pill, and Dr Stephanie Snow, a descendant of John Snow, who discovered anaesthesia in the 1800s.
Professor Johan Mackenbach of Erasmus University Medical Centre, Rotterdam, the Netherlands, championed sanitation.
He said: "I'm delighted that sanitation is recognised by so many people as such an important milestone.
"The general lesson which still holds is that passive protection against health hazards is often the best way to improve population health."
The original champions of the sanitary revolution were John Snow, who showed that cholera was spread by water, and Edwin Chadwick, who came up with the idea of sewage disposal and piping water into homes.
During the mid-19th century cholera epidemic, John Snow showed that shutting off a particular pump in London stopped the spread of cholera in that area.
Edwin Chadwick came up with the idea of sewers and piped drinking water linked to people's living accommodation, to cut the risk of infection from poor urban drainage.
His ideas were eventually accepted and between 1901 and 1970, deaths from diarrhoea and dysentery fell by around 12% in the Netherlands and England and Wales.
Still a problem
However, Professor Mackenbach said: "Inadequate sanitation is still a major problem in the developing world.
"In 2001, unsafe water, sanitation and hygiene accounted for over 1.5 million deaths from diarrhoeal disease in low and middle-income countries.
"Clearly, sanitation still plays a vital role in improving public health now and in the future."
Dr Fiona Godlee, BMJ Editor said: "The response to our poll has been overwhelming, it is deeply heartening to see science and medicine provoke such passion and debate.
She said selecting just one winner was "always going to be difficult," and before the contest said: "Any of these milestones would make a deserving winner - they have all made an enormous contribution to society and made a difference to millions of lives."