First, I want to point out that I recognize that I am in a very good position relative to many in this economy. Having an option between two organizations is a luxury that most do not have. That said, I am 24 years old, holding a liberal arts degree from an undistinguished university and have worked for the last three years in a small (~50 employees) software firm doing project management. I say this to illustrate how lucky I am to have received these offers in the first place. I have been job searching for some time with increasing urgency as the company at which I presently work appears to be floundering financially. I was contacted by a recruiting agency that is soliciting a position for a Fortune 50, Company A (think Wal-Mart). This position is for an internal consultant working in project management on a multi-year contract. I have gone through two rounds of interviews onsite and am intrigued by the work and thrilled by the potential to work for this organization. The interview process is very long, however, and I have been in it for several months. During the interview process for Company A, I was contacted by a recruiting agency for Company B. Company B is also Fortune 50. The position would be to run two projects in a project management capacity for a ~6 month contract, with the possibility of extension. The offer was exploding, and upon hearing even worse news from my current employer, I took the offer. I received a final round invitation from Company A, and am planning to attend the interview. The interview will take place on Friday, I am scheduled to begin work at Company B the following Monday. The essence of my question is this: if I were to receive an offer from Company A, the company of my dreams, would I be making a big mistake by informing Company B that, after working there for only a few days, that I received an offer that I could not turn down and would therefore be putting my two weeks notice? My concerns here are for the health of my career, the potential concerns that Company A might have if they heard about what I did to Company B, etc. The money at the two places is the same. The level of responsibility is much higher at A, and the brand name is much, much larger, and the contract is for much longer, thereby giving me much more security. I feel miserable at the prospect of putting Company B in a bind, but it is difficult to see how I could forgive myself for foregoing such an opportunity. Any and all thoughts appreciated.