A method and system for buying and selling media advertising units over a distributed communication network, such as the Internet, provides a server on network including a database containing information pertaining to available advertising units, such as advertising time slots in television programming schedules, provided by media content providers. The server provides buyers of the advertising units access to the database over the network, whereby buyers may search the database and make bids to the sellers for selected advertising units. Sellers of advertising units access the database over said network to enter the information, receive bids entered by buyers, accept bids, and enter contracts into the server for communication to buyers over the network.