In part 1, we examined the effectiveness of the Athlete Biological Passport (ABO) since its cycling rollout in 2008 and sport-wide rollout a year later. We ended by focusing on the mooted modern-day scourge of the ABP – separating legal altitude-induced changes in a cyclist’s blood profile and illegal micro-dosing EPO blood profiles. Here, we investigate the issue at hand and what the testers are doing about it…