The actor admits he was inundated with free gifts after landing the role of villainous Pete Campbell in the TV drama - and decided to clear out his one-bedroom Hollywood home to get rid of the clutter.
And the habit has become so extreme, Kartheiser now doesn't own a car, a mirror or a lavatory.
He explains, "It started a couple of years ago. It was in response to going to these Golden Globe-type events and they just give you stuff. You don't want it. You don't use it. And then Mad Men started to become a success on a popular level and people started sending me stuff, just boxes of s**t. Gifts for every holiday, clothes.
"One day, I looked around and thought, 'I don't want this stuff, I didn't ask for it.' So I started giving it to friends or charity stores, or if it is still in its box I might sell it for a hundred bucks. I liked it so I didn't stop.
"I don't have a toilet at the moment. My house is just a wooden box. I mean, I am planning to get a toilet at some point. But for now I have to go to the neighbours. I threw it all out."