A man has been taken to hospital with upper body injuries after being assaulted at the Caulfield Cup, one of the country's biggest race days.

A Victoria Police spokeswoman said a suspect had been arrested and was assisting investigators with their inquiries.

She said four others had been arrested for being drunk, but overall police were pleased with crowd behaviour.

The assault victim was taken to The Alfred hospital with non-life threatening injuries.

He is in a stable condition.

An estimated 40,000 people attended the races.