Enron Corp. and Blockbuster Inc. unexpectedly terminated an exclusive 20-year agreement under which the two companies were to jointly deliver video-on-demand to consumers' homes via Enron's fiber-optics network. Instead, executives at both companies said they would pursue video-on-demand services on their own or with other partners.

The much-heralded relationship between energy giant Enron and video-rental chain Blockbuster was struck just eight months ago, and was expected to be the jumping-off point for offering a variety...