The world's biggest horse race attractions millions of pounds of bets but remains hugely controversial.
Why is the Grand National so dangerous?
On Saturday, 40 horses will jump 30 fences over a course that spans nearly four-and-a-half miles.
Fourteen of the fences are jumped twice and fences and 16 are jumped once.
It's the most gruelling course in the British racing calendar and horses have had to pass strict tests to get to the startline.
In fact, this is one of the main changes to improve horse safety. The requirement to enter means runners to have been placed fourth or better in a previous recognised steeplechase over a distance of at least three miles.
Eleven horses have died in the Grand National since 2000
The famous event still attracts widespread controversy
How many horses die at the Grand National?
Deaths in horse racing remain relatively rare – there is an average of one death every 250 races.
But the Grand National figures are far worse – yielding seven fatalities out of 439 horses taking part between 2000 and 2010.
Has anything been done to make it safer for horses at the Grand National?
Animal rights campaigners say the famous Aintree racecourse is “a significant killer of horses” – despite fences being reduced in height.
Grand National 2017: Fashion arrivals
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Grand National at Aintree 2017 is here and hundreds of well-dressed racing fans have flocked to the racecourse in their Sunday finest.
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Although this, some argue, may have not had a positive effect on horse safety at all.
One theory goes that the lower fences actually put horses in more danger because it encourages horses to run faster.
During the 1970s and 1980s, 12 horses died at the Grand National. Following the changes in fence height, 17 horses died in the next 20-year period from 1990 to 2010.
When did the last horse die at the Grand National?
In recent history, the record is a little better. No horse has died in the National since Synchronised, in 2012, following a fall at Becher's Brook.
Becher's Brook, incidentally, remains the most dangerous jump in National history. Fourteen horses have died at the jump in National history.
Animal Aid say the positioning of Becher's Brook and its angle are both problematic for horses. It is not jumped head-on so jockeys tend to steer their mounts to the nearside – creating an even bigger angle.
The Grand National is the most gruelling course in the British racing calendar
During the three-day Aintree carnival last year, six horses died as a direct result of racing.
And since the turn of the millennium, 48 horses have died at Aintree – at an average of three a year.
In January, former Grand National winner Many Clouds died of a suspected heart attack at the Cheltenham Festival trials day.