Negotiating parties oftentimes do not reach mutually beneficial agreements. A considerable body of research on negotiation analysis compiled a set of so called common biases in negotiations that systematically affect the cognition and behavior of negotiators and thereby influence agreements (e.g. Bazerman and Neale 1992; Bazerman et al. 2000). The present work adds an additional effect, the attachment effect. This effect biases decision makers in bilateral multi-issue negotiations and influences their preferences via reference points--negotiators get caught in a kind of negotiation fever.