A woman was taken to hospital after being assaulted by a man in Buxton at the weekend.
The incident is believed to have happened in Terrace Road at around 3.50am.
She suffered facial injuries, which required hospital treatment.
On Sunday, police tape could be seen around buildings on Market Place as police carried out enquiries.
A Derbyshire Constabulary spokesperson said: "The man is described as around 35-years-old, with short hair and was wearing a hoodie.
"Anyone who witnessed the incident, has CCTV installed in the area or was driving nearby with dashcam is asked to contact Derbyshire police via the force's social media accounts or by calling 101.
"Please quote reference number 19*295921 and the name of the officer in the case, DS Chris Simcock, in any correspondence."