In this chapter, core doctrines of competition law generally applied by national authorities are reviewed. Most competition laws examine anti-competitive behavior in relation to agreements between enterprises, on the one hand, and monopolization or abuse of dominant position, on the other. Anti-competitive activity is further viewed as either 'horizontal' or 'vertical'. Horizontal anti-competitive activity refers to conduct among independent enterprises that are suppliers of competitive (or potentially competitive) goods or services. Vertical anti-competitive activity refers to the supply chain controlled by a producer, beginning with inputs to production, into production, intermediate distribution and, ultimately, the retail sale of goods or services. Some types of agreement between enterprises are so inherently anti-competitive that proof of the existence of the agreement is sufficient to establish a violation. Such agreements are referred to either as per se anti-competitive or hard-core competition law violations. Other types of conduct that may seem anti-competitive on their face may also have a pro-competitive justification, such that competition authorities assess the balance. This balancing is often referred to as assessment under the “rule of reason”. For a competition law violation to be found, the anti-competitive aspect of the arrangement should outweigh potential pro-competitive benefits. Examples of horizontal anti-competitive behavior that are per se illegal in most jurisdictions include price-fixing among competitors, output restraints and allocation of geographic territories. Examples of vertical restraints that are per se illegal in many, but not all, jurisdictions are resale price maintenance (or fixing the minimum price at which retailers may sell) and “exclusive grantback” requirements in patent licenses. There are some significant risks of anti-competitive conduct in pharmaceuticals markets that are fairly widespread and deserve close attention from competition authorities. These include bid manipulation in procurement of health technologies, whereby a group of potential competitors may agree not to submit bids below a set price and to allocate the 'lowest set price' bid to a particular firm. Such activity may also involve inappropriate payments to government officials who might otherwise report the anti-competitive practice. Anti-competitive conduct by patent-owning enterprises may include requiring a distributor or retailer of health technologies to purchase a complete line of products as a condition of purchasing a particular product or products (i.e. a tying arrangement). Perhaps the most widely discussed form of anti-competitive conduct involving patent owners involves 'buying out' generic challenges to patents that might otherwise result in generic products entering the market at an early date. Such buyouts upset the balance legislators strive to achieve between granting patents and authorizing their challenge to foster competition. Mergers and acquisitions may adversely affect product markets by, for example, allowing combined companies to raise prices for therapies previously in competition with each other. Anti-competitive conduct affects markets for innovation, such as when a patent is illegitimately used to prevent the development of new products not within the scope of the patent, or when patent-owning companies combine to control markets. Mergers and acquisitions can affect markets for innovation by reducing potential R&D targets and opportunities. As noted earlier, competition law addresses dominant enterprises and monopolies as well as agreements between enterprises. A single enterprise (or a small group of enterprises) may alone exercise such significant power in a relevant market as to be able to raise prices above competitive market prices without concern that others will enter the market and undercut it. When an enterprise dominates a market, it does not need consensual agreements with potential competitors to control them; it may unilaterally dictate terms. One objective surrounding the control of mergers and acquisitions is to prevent an enterprise from combining with others precisely to take a dominant position in the market. This chapter concludes with a discussion of the types of remedies that are available to national authorities and private parties as redress for anti-competitive conduct. It is not uncommon for the government to enter into some form of settlement agreement with an accused enterprise pursuant to which that enterprise agrees to cease its anti-competitive activities and may also make a payment either as damages or as a penalty. Such settlements may be approved and/or supervised by courts. In some jurisdictions, particularly the United States, a good deal of competition enforcement is undertaken by private actors suing for damages. Anti-competitive conduct may also be subject to criminal penalties including substantial fines, and imprisonment for individuals. Specific types of remedies may be used to address anti-competitive conduct that is undertaken to block the introduction of generic products. This may include requiring pharmaceutical patent owners to compensate public procurement authorities, generic producers and others for damages occasioned by the unwarranted invocation of patents. Strong consideration should be given to prohibiting patent owners from “buying out” generic producers' challenges to patent validity or assertions of non-infringement. Other types of specific remedies may be considered.