Traditional Chamorro freshwater use customs on Guam still exist, at least in the recollections of Chamorros above the age of 40, if not in actual practice in the present day. Such customs were analyzed in both their past and present contexts, and are documented to provide possible insights into more effective systems of acquiring and maintaining a sufficient supply of freshwater on Guam. Archaeological evidence suggests a close correspondence between prehistoric settlement patterns and freshwater sources. It is speculated that pre- and post-contact Chamorros living in the northern plateau of Guam may have been involved in reciprocal trading arrangements with sites that had freshwater readily available during dry periods. The perception of freshwater in the Chamorro language context is shown to be changing. Ethnohistorical studies indicate that availability of freshwater to meet the needs of Guam's people has always been a problem. Sociocultural studies, as gleaned from the questionnaire, on the other hand, suggest that Chamorros over the age of 40 do not recall problems for the most part in their water supply systems of the past. Chamorro informants tend to identify their villages of residence and traditional water sources by locally derived names that are not often found on present-day maps of Guam. Further studies on the theme of freshwater use customs on Guam are recommended.