More than 900 women are taking part in the Martlets Midnight Walk.
They began leaving Brighton Racecourse at about midnight when Councillor Bill Randall, the mayor of Brighton and Hove, set them on their way.
Many of them are wearing bunny ears, pink hats or wigs, tutus or deely boppers.
The event is organised to raise funds for the Martlets Hospice, in Hove, which cares for people with a terminal illness.
The hospice is not funded by the NHS and relies on generating more than £4 million a year, most of it raised by events such as the Midnight Walk.
This year the Martlets is one of the mayor’s charities.
On Wednesday (20 June) the Martlets Hospice is holding a volunteer information and recruitment day from 10am to 4pm in Wayfield Avenue, just off Holmes Avenue.
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