Cat problem

Hi to all!

I've had my cat for going on 15 years.
He's my buddy and I think the world of him, but when he uses his litter
box; 3 out of 5 times he will drop feces either right at my bathroom
door or in front of the box. I'd say that this has been happening for
about three years.
One time I had company (I was just coming home) who went (in ahead of
me) to use my bathroom and stepped right in it. I can't tell you how
embarrasing that was.
When I'm home; I can certainly tell when "it" not in the box, because
wheew!!
I keep his litter box clean, so I don't understand.
I would appreciate ANY ideas.

Thanks!

Kermit