Well, it can be tricky. In a short-sale, even though there is a homeowner, the bank technically is the seller. It's within your right to renegotiate the offer price but, given it's a short-sale the bank may or may not take less money since they're already losing money. You could also face making the approval process take longer if they have already agreed to your offer price. If you have the time to wait, you can certainly renegotiate and now that the home-buyer tax credit is extended until April, your not in any immediate rush. My opinion would be to consult with your agent on the banks involved in the short-sale. Some banks are easier to work with than others as you can imagine.