Police are appealing for public assistance to help locate missing man Thomas.
The 27-year-old was last seen at a residence on the Maroondah Highway, Lilydale, about midday on Monday 11 July.
Police and family are concerned for Thomas as he has a medical condition and his disappearance is out of character.
Thomas is Caucasian, of solid build, with short brown hair.
He was last seen wearing a maroon-coloured hooded jumper and dark navy denim jeans.
Thomas is known to frequent public transport.
Police have released an image of Thomas and urge anyone with information on his whereabouts to contact Lilydale Police Station on 9739 2300.
