Dr Mark Porter unpicks the science behind the so called 'weekend effect'. Politicians have quoted research claiming that people are 20% more likely to die of a stroke at the weekend, while another much cited study finds 11,000 more deaths in people admitted at the weekend. But how valid are these figures and the research that generated them? Dr Margaret McCartney reviews the stroke data that has been criticised by experts as being out of date. While Mark Porter talks to Editor of the BMJ, Fiona Godlee, who published the 11,000 figure but is concerned about the political use of the findings. And discusses the study with lead author Nick Freemantle, plus Consultant Surgeon Sam Nashef who is sceptical about the results.