This chapter explains the intricacies of hair comparison and its history. First, the cases of Australian Colin Ross in 1922 and Canadian James Driskell in 1984 are presented to exemplify the failure of microscopic hair comparison evidence. There have been several wrongful convictions caused, at least in part, by flawed or exaggerated microscopic hair comparison expert testimony. In the US, the FBI has been under fire because testifying agents have overstated the value of hair evidence. In some instances, hair analyses that were correctly conducted and accurately reported to courts and juries have resulted in the convictions of innocent defendants. The chapter contains a review of the history of the use of hair as evidence and a primer on the characteristics and classification of hair, and then concludes with a discussion of the need for continued reliance on appropriately weighted microscopic hair analysis evidence in conjunction with mitochondrial DNA (mtDNA) testing to ensure the best legal outcomes.