Agat Harbor, Guam, was selected for monitoring under the Monitoring of Coastal Projects Program, which is sponsored by Headquarters, U.S. Army Corps of Engineers. During a 3-year observation period, the following data were collected: a. Directional energy spectra and surface winds from an offshore site. b. Energy spectra at several locations on a shore-normal transect across the reef flat. c. Wave conditions and water elevations at the structure and harbor response during large wave events. d. Directional energy spectra at the outer boundary of the model and at several sites within the harbor. e. Energy spectra at the outer and inner ends of the channel. f Periodic site inspections and aerial photographs of the harbor and surroundings. Most of the quantitative objectives of the study were not met because of the lack of measured data during high-energy events. However, observations have resulted in valuable qualitative information that should be considered when planning or designing projects in a similar environment.