Michael Rosse was last seen at his home at around 10.30am today (July 31), said Sussex Police.
The 60-year-old is described as white, 5ft 8ins, with short black hair and blue eyes. He was last seen wearing a long-sleeved dark blue shirt, blue jeans and brown shoes.
Michael takes regular medication and it is not believed he has taken any with him.
If you see him call 999 immediately.
If you have information on where he could be or any previous sightings report online or call 101 quoting reference 648 of 31/07.