Transit Crime Investigation Unit detectives are appealing for public assistance following a sexual assault on a bus in Thomastown this month.
Investigators have been told a woman was at a bus stop on Alexander Avenue about 9.50am on 10 November.
The 57-year-old woman was approached by an unknown male who made explicit comments towards her before following her onto her bus.
He sat next to her and sexually assaulted her before getting off the bus at Thomastown Railway Station and boarding another bus towards Epping.
Detectives have released CCTV and images of a man who they believe can assist with their enquiries.
The man is perceived to be Caucasian with tanned skin, slim build, approximately 80-85-years-old with short grey hair.
He was wearing dark brown coloured pants with a sewn rip above the left knee, light brown collared t-shirt, black leather shoes and a gold coloured wristwatch.
Anyone with information is asked to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report at www.crimestoppers.com.au