A 50-year-old woman was sexually assaulted.
The woman was walking in Titmus Drive, Crawley, close to the allotments when a man groped her.
She pushed the man away and managed to escape.
The incident occured at around 10pm on June 5.
PC Claudia Fornari said: "The victim has been left extremely upset by her ordeal. I need to speak to anyone who was in or around Titmus Drive on Wednesday night and could have seen or heard something.
"The victim screamed for help so someone may have been disturbed by the noise and gone to check what had happened.
"If you know anything at all, please contact us."
Anyone with information should call 101 quoting serial 1666, email firstname.lastname@example.org or call the independent charity Crimestoppers anonymously on 0800 555111.