The previous chapter examined the possibilities of introducing competition into markets where, because of technical or institutional constraints, effective competition has been either completely absent or stifled. The other main area of competition policy is that of maintaining competition in markets where the main problems are the restrictive practices of a number of firms acting together and the anti-competitive behaviour of firms that hold dominant positions in their markets. In this chapter we first give a brief overview of competition policy in the USA, UK and European Communities, before going on to examine restrictive practices policy in more detail. Section 15.2 describes the different types of restrictive practices. Section 15.3 examines policy towards horizontal collusive behaviour in the UK, EC and USA, and this is followed in section 15.4 by a review of policy approaches to vertical arrangements between firms.