Don't burn any bridges, be firm and professional. "Sorry, I have accepted a position with another company/hospital/whatever." OR... you could ask for a better offer. Respectfully say that "I'm currently considering an offer from another place." Then toss-out something that might make you re-consider.. "Maybe we could talk about a signing bonus if I stayed here?" (make sure that what you ask for is possible, don't ask for an extra week of vacation or $3/hour more if those are already specified by some sort of collective agreement, for instance). As for being disrespectful to the first job offer, ask yourself if you think they feel any loyalty to you? Or will they let you go the day after it makes economic sense for them to do so? Speaking personally, I feel loyalty to those that demonstrate loyalty to me. It's a cold and mercenary world out there and it's up to you to make the best decisions about you and your future that you can, using the best information you have. Good luck. //// Edited to add, never tell them who you are going to work for when you leave. If they don't already know, it's none of there business.