The Government of Guam's Long-term Coral Reef Monitoring Program, coordinated by the Guam Coastal Management Program until October 2013 and now coordinated by the University of Guam Marine Lab, involves the collection of data for a suite of coral reef ecosystem health parameters at several high priority reef sites around the island of Guam, including Tumon Bay, East Agana Bay, Piti Bay, and Western Shoals. Sites at Fouha Bay, the Achang Reef Flat Marine Preserve, and the Eastern seaward slope near Cocos Island will be established in 2014. Data are collected annually or biennially by a team of highly-trained field biologists from the Guam Coastal Management Program, the NOAA Pacific Islands Regional Office, the University of Guam Marine Lab, and with occasional assistance by staff from other agencies. Macroinvertebrates are culturally, economically, and ecologically important resources for the island of Guam. In recognition of the value and importance of this resource, macroinvertebrate surveys are a key component of the Guam Long-term Coral Reef Monitoring Program. Macroinvertebrate surveys have been conducted at high priority reef sites around Guam since August 2010. The surveys are carried out at numerous sampling stations within each monitoring site, the locations of which were generated randomly using a Geographic Information System and the relevant bathymetric and benthic habitat data. A split-panel approach is currently used for the sampling design, with half of all sampling stations in a given site being fixed and half re-randomized every visit or every other visit. The monitoring team counts the number of commercially and ecologically important macroinvertebrate species within a 4 m x 25 m belt transect at all stations (except at the Western Shoals stations, where 4 m x 15 m belts are used). The longest dimension of Tridacna individuals is also recorded. These monitoring data on macroinvertebrate communities provide results on macroinvertebrate density and diversity, allow for exploration of community structure by functional group; and can be used to detect changes in macroinvertebrate communities over time.