Auction is a procedure for allocating resources with good results. I present the theoretical literature on auctions, which shows that, under several conditions, auctions led to allocate resources efficiently and to maximize the auctioneer’s income. However, these results are only valid if the participants of the auction are not organized in cartels. A cartel is an organization which inhibits business competition among firms. Acting as a cartel may or not lead to an effi- cient allocation of resources, however the auctioneer’s income, will always suffer. I analyze the theoretical literature regarding cartels in auctions of a single object, which characterizes ways of coordination and act5ion strategies and their sustainability. In addition, I analyze the challenges that a cartel should overcome. Also, I present measures the auctioneer should take in case there is a suspicion of an existing cartel. First-price auction is the least susceptible to the action of cartels, because there is an incentive for firms to divert from cartel guidance. Combating cartels is evaluated by the discount rate necessary for the existence of a cartel. If the discount rate needed is smaller it means that this cartel is more difficult to be sustained. Moreover, I show that a random reserve price is a better way to fight against cartels than a fix reserve price in repetitive first-price auctions.