The athlete biological passport (ABP) is an established means for longitudinal monitoring of selected individual biomarkers of an athlete to obtain indirect but potentially long-term indications of the use of substances or methods prohibited in sport. Along the change from population-based reference values to individual profiling, the ABP aims at triggering follow-up investigations concerning the potential use of endogenous substances with doping potential, which might be difficult either to identify with the existing analytical methods or to interpret based only on the results of a single biological sample. The ABP program has been on-going within the World Anti-Doping Agency (WADA) management since 2009, when the hematological module was officially established to discover blood doping practices, such as administration of erythropoietin (EPO) or application of blood transfusion. Since 2014, the ABP has been complemented by the steroid module, with the aim of targeting the prohibited use of testosterone and other endogenous anabolic androgenic steroids with performance enhancing or masking capability. Although the main objective is to guide and assist the anti-doping organizations in their test distribution plans, the ABP may also be used to proceed with a case to an anti-doping rule violation. Evaluation of biological markers, especially in distinguishing between doping from other confounding factors, requires high level and diversity of expertise, which is coordinated by the athlete biological passport management unit (APMU). Since 2019, the WADA accredited anti-doping laboratories are defined as the host organizations for the APMUs. The benefit of such a structure is to obtain a fully anonymous evaluation process for the passports and an additional level of expertise for the interpretation of analytical results as well as to have a fluent communication line with the analyzing laboratories when further details are needed for the analytical testing and documentation.