Brighton's 2010 Pride celebration was the biggest in its 18-year history, with more than 160,000 people taking part in the festivities.
Sussex Police said Saturday's event was peaceful and successful, with very few incidents.
The parade left the seafront at 1100 BST and made its way to Preston Park, where the event continued until the evening.
By 1800 BST, 20 arrests had been made for drug and public order offences.
About 100 people had been treated by St John Ambulance, the majority for alcohol-related issues.
St John Ambulance said it dealt with about 220 casualties in all, including those needing treatment during the St James Street celebrations which went on to the early hours of Sunday.
Most casualties were treated at the scene but 11 patients had to be taken to hospital.
About 50 police officers, staff and supporters led the carnival parade for the seventh year running.
"Once again, people have attended in their thousands to line the streets and take part in the Pride celebrations," said Supt Steve Whitton.
"I'd like to thank all the organisers, the emergency services and all the participants for making the event such a great success."
Before the event, police said they had made a "significant dent" in the illegal drugs trade surrounding Pride.
A 50-year-old suspected drug dealer was arrested on Friday in Gloucester Road.
Police raided a house and confiscated 15lb (7kg) of a substance believed to be ketamine and more than £60,000 in cash.
Ch Insp Laurence Taylor said it was believed the drugs were intended for distribution at Pride, and would have had a street value of about £140,000.
Last year St John Ambulance dealt with a number of casualties at Pride as a result of ketamine.
The theme of this year's Pride, which had to be rescued from financial difficulty by Brighton and Hove City Council, was Pride and (No) Prejudice, with many revellers dressed in Regency costume.
Its future as a free event was secured in January after the organisers received a £20,000 loan to help meet a £50,000 deficit.
Brighton and Hove Pride said it cost over £250,000 to put on the one-day event, and the charity appealed to people attending to donate to bucket collections on the parade route and at the park.