Police are concerned for the safety of Michael Fraser Rosse, 79, who left his home in Warninglid, near Haywards Heath, at midday on Saturday (12 May).
Michael suffers from anxiety and depression and is therefore considered vulnerable, although physically fit for his age.
He is white, 5'7", with greying black hair, a fair complexion and of stocky build. He was last seen wearing a dark blue bomber jacket, blue trousers and brown shoes.
Anyone seeing Michael or who may know of his whereabouts is asked to contact Sussex Police online or by phoning 101, quoting serial 604 of 12/05.
If he is thought to be ill or in danger, please dial 999 immediately and ask for police.