Filaments are cold surface features often found in eastern boundary current regions. A typical filament originates near the shelf and extends as a narrow (100 km or less) tongue extending hundreds of kilometers offshore. These features represent the main focus of the the Coastal Transition Zone program, which took place in 1987 off the northern coast of California. The historical background for the program is discussed, as well as the questions that motivated it. The general approach of the program is described, followed by an overview of the initial findings, representing a summary of our current understanding of these features and their relation with eastern boundary current dynamics. ¿ American Geophysical Union 1991