The serving of advertisements with (e.g., on) video documents may be improved in a number of ways. For example, a system may (a) accept information defining at least one ad spot associated with at least one instance of an video document, (b) accept offers to have advertisements served in the ad spot(s), and (c) arbitrate among competing advertisements, using at least the offers, to determine at least one advertisement to be served in that ad spot(s). As another example, a system may (a) accept relevance information for an advertisement, (b) determine at least one video document using the accepted relevance information, (c) present information about the video document(s) to an advertiser associated with the advertisement, and (d) accept, from the advertiser, an offer to have its advertisement served with at least one of the video document(s) accepted. As yet another example, a system may (a) accept relevance information for an video document, (b) determine a plurality of advertisements relevant to the video document using the relevance information and serving constraints of the advertisements, and (c) select at least one of the determined relevant advertisements to be served with the video document. Examples of video documents include video files published on the Internet, television programs, live or recorded talk shows, video-voice mail, segments of an video conversation, etc.