Trevor Downes, 49, was last seen at his home at 9.30am yesterday by a relative.
Police are appealing for information about the and describe Mr Downes as white, with a tanned appearance, about 6ft 1ins, and has short dark hair.
Mr Downes has links to Easthampstead, Aldershot in Hampshire and Cardiff in South Wales.
Investigating officer, Insp Tracey Croucher, said; “We are becoming increasingly concerned about Mr Downes’ welfare and are appealing for anyone with information about him to contact police immediately.
“We do not believe Mr Downes has access to any funds or transport and would like to hear from anyone who believes they have any information about his whereabouts.”
Thames Valley Police would like to hear from anyone who has information about where Mr Downes may be, or anyone who thinks they may have seen someone matching his description.
If you have any information please contact the Thames Valley Police Enquiry Centre on 101 quoting URN 1458 of 3/9.
If you do not want to speak directly to the police you can contact the independent charity Crimestoppers anonymously on 0800 555 111 or online at www.crimestoppers-uk.org. No personal details are taken, information is not traced or recorded and you will not go to court.