Extra water was available this year and organisers have said air quality was fresher after high pollution on Friday.
Organisers said 9,426 people started this year's race.
Kenyan Duncan Maiyo, 24, won the men's race, setting a new personal best time of two hours 34 minutes and 25 seconds, while compatriot Pennina Wanjiru, 30, won the women's race in 2:34:25.
Spokesman Michael Butcher said the event had gone very well and the atmosphere was "fantastic".
The runners had a slightly chilly start and conditions were windy, but the weather was beautiful, he added.
"Thousands of people are out there now. I went to the finish line and had to walk along the course because it was impossible to get on to the pavements," he said.
Race director Tom Naylor said people travelled from across the world to take part, including 14 who had come from Australia.
"Once you've done one marathon, maybe New York or Berlin, then the running tourist wants more events," he added.
He said: "It's a fantastic tourist destination. The course is great - nice and flat and fast. It takes in the best parts of the city, and who wouldn't want to come and do Brighton Marathon?"
Two years ago, a runner collapsed and died while taking part in the race, partly from dehydration.
Mr Naylor said this year water was provided at 21 stations, one at nearly every mile of the course.
"It means runners can drink more often which means they can drink less at each water station, which is much better for the body and much better for their performance," he said.
Thousands of people have taken part in the Brighton marathon with top athletes competing alongside first-timers.