Antidoping laws exist to provide a safe and fair environment for participation in sport. These laws should prevent and protect athletes from subjecting themselves to health risks through the use of unsafe, but performance-enhancing compounds. An area of major controversy is the "sports supplement" industry, which is poorly regulated when compared with prescription drugs, but yet is a potential source of doping violations. In this regard, pharmacokinetic characteristics, easy availability through the chemical industry and low costs would make cobalt administration the ideal surrogate or complement for rHuEpo administration, turning out to be the most suited blood doping technique for athletes seeking to improve aerobic performances with little chance of testing positive. At variance with blood doping, cobalt is not mentioned in the WADA prohibited list [
14]. Nevertheless, the definition of blood doping currently includes the use of autologous, homologous or heterologous blood or red blood cell products of any origin, other than for medical treatment, and each means artificially enhancing the uptake, transport or delivery of oxygen, including but not limited to perfluorochemicals, efaproxiral (RSR13) and modified hemoglobin products (hemoglobin-based blood substitutes, microencapsulated hemoglobin products). Thus, cobalt may be quantified through the use of bioassays that are comprised of either in vivo and/or in vitro measurements, though in vitro analyses are routinely performed in situations where in vivo analyses can not be obtained or in support of an in vivo monitoring program. Available techniques for measuring whole blood, serum, plasma or urinary cobalt involve analytic approaches, such as electrothermal atomic absorption spectrometry, extractive spectrophotometric determination, differential pulse anodic stripping voltammetry, neutron activation analysis, inductively coupled plasma-atomic emission spectrometry and x-ray fluorescence and gas chromatography-mass spectrometry [
16‐
18], most of which are currently not practical for antidoping laboratories. Then, the little information available so far on cobalt metabolism in athletes hampers the appropriate interpretation of population data and the analysis of potential doping cases. Additional testing strategies, relaying on the identification of indirect biological effects of cobalt chloride administration such as activation of vascular endothelial growth factor (VEGF) gene transcription [
19] or enhanced synthesis of delta-aminolevulinate [
20], may be reliable alternatives, but will necessary entail a long and demanding process of clinical and analytical validation. More research on cobalt metabolism in athletes is compelling, along with implementation of effective strategies to unmask this potentially deleterious doping practice.