A system and method for delivering channels of presentation streams carrying targeted advertisements in a television service network environment. The system includes a generator for generating a set of presentation streams for each of programming channels, each of the presentation streams in each set having same programming data but different ads directed to advertiser-specific market segments of different advertisers. A plurality of local routing stations receive the generated sets of presentation streams. At least one local routing station processes the sets of presentation streams and selectively switches between the presentation streams in each set to output one presentation stream for a programming channel. As a result, a presentation stream carrying the most appropriate ad is provided to a viewer at any given time for at least one programming channel.