The Hawai'i Coral Reef Assessment and Monitoring Program (CRAMP) was established to describe the spatial and temporal variation in Ha- waiian coral reef communities in relation to natural and anthropogenic factors. Sixty permanent reef sites stratified by depth have been monitored in the main Hawaiian Islands since 1999 and formed the basis for analysis of temporal change over the initial 3-yr period. A rapid assessment technique (RAT) was developed to supplement the monitoring site data and provide much wider geographic coverage, but with a focus on spatial patterns rather than temporal change. Analysis of these data supports and amplifies the results of many other ecological studies on Hawaiian reefs. The data revealed that the major natural factors influencing reef coral community structure in Hawai'i include depth, wave height, wave direction, island age, rugosity, and sediment grain size. Pos- sible anthropogenic influences and trends also appeared in the data. Areas of decline appear to be concentrated on islands with high human population or in areas suffering from extensive sedimentation. Reefs receiving high terrigenous runoff contain sediments with high organic content. Spatial analysis showed an inverse relationship between percentage organics and coral species richness and diversity. Reef coral communities can undergo natural oscillations over a period of years, so continuation of the CRAMP longer-term monitoring is required to establish long-term (decadal) environmental trends.