For more than a decade, the scientific literature has stressed the preeminence of pre-analytical error. Often these papers play a zero-sum game, emphasizing pre- and post-analytical quality while diminishing the importance of analytical quality. In this lesson, sources of errors for the pre-analytic and post-analytic phases of the Total Testing Process are discussed, along with possible solutions. Finally, the occurrence of these errors are rated on a Sigma-scale, to put pre-analytical problems into context with analytical performance. (Preview)