Have him checked for a urinary tract infection. This must always be done
firstly.
Gail

<sigh>
Take the cat to the vet to rule out UTI.
Search the Google archive for "inapropriate elimination" - you will
find many suggestions.

-L.
(This is now going to become my standard response...)

Very basic question here........

You say he is male, is he neutered?  Un-neutered male cats will often
mark their territory.  If he is not neutered, get him neutered.  This
may or may not solve the problem, because marking starts out as an
instinctive behavior, but can become a habit if carried on for too
long.

Other things too can trigger this behavior like a recent move to a new
home, or an introduction of another cat into the environment.  I had a
female cat that used to spray when we moved (which we did three times
in her lifetime).  Eventually when she became comfortable she would
stop.  If the cats spraying is anxiety related, the vet may reccommend
an anti depressant medication for him.