The research literature on negotiation has advanced greatly by identifying the key shortcomings of negotiators. These shortcomings have been broadly construed as systematic biases held by negotiators that affect the processes and outcomes of negotiation (Neale & Bazerman, 1991; Thompson & Nadler, 2000). The key questions that negotiation researchers have examined in the area of bias have centered on three key issues: (1) the biases that affect judgment and behavior in negotiation; (2) their psychological underpinnings, such as motivation, cognition, emotion, etc.; and (3) the conditions or situations that augment or reduce bias. Accordingly, this chapter examines the nature of bias in negotiation and the conditions under which bias is intensified or ameliorated. We distinguish four types of biases: cognitive biases, social perception biases, motivational biases, and emotional biases. We examine current conceptualizations of bias and the implications for theory and practice.