"Up to 80% of all option ARM [home loan] borrowers make only the minimum payment each month, according to Fitch Ratings. The rest of the money [owed] gets added to the balance of the mortgage, a situation known as negative amortization. And once balances grow to a certain amount, the loans automatically reset at far higher payments. Most of these borrowers aren't paying down their loans; they're underpaying them up."

In other words, the so-called "minimum payment" is not enough even to cover the interest. What a great deal!

See: Business Week article (2006-09)