Tournament selection is a popular form of selection which is commonly used with genetic algorithms, genetic programming and evolutionary programming. However, tournament selection introduces a sampling bias into the selection process. We review analytic results and present empirical evidence that shows this bias has a significant impact on search performance. We introduce two new forms of unbiased tournament selection that remove or reduce sampling bias in tournament selection. Categories and Subject Descriptors I.2.8 [Artificial Intelligence]: Problem Solving, Control