Public bidding is a common mechanism used by states to promote competition in public procurement. However, the competition generated by public bidding may be blocked by two anticompetitive practices: collusion and corruption. Two different problems with a common effect: that the public contract will not be awarded on the basis of merit or efficiency, thereby affecting competitive- ness. This paper analyzes the tools available for the Colombian competition agency for fighting collusion and corruption in public bids. We highlight the importance of strategic assistance to public agencies by the competition office at the moment of designing and executing the bidding process, in accordance with international recommendations.