Police are appealing for public assistance to help locate missing man Riley.
The 22-year-old was last seen in Werribee on 15 September.
Police and family hold concerns for his welfare due to a medical condition.
Two images of Riley have been released in the hope someone recognises him and can provide information on his current whereabouts.
Riley is described as about 180cm tall, of a medium build with black hair.
He was last seen wearing a black beanie, black jacket and green pants.
It is believed he may be in the St Kilda, Melton or Werribee areas.
Anyone who sees Riley is urged to contact Werribee Police Station on 9216 7480.