Field measurements for the Hunter Region Acid Rain Project were conducted as a major cooperative effort by the New South Wales State Pollution Control Commission, the Electricity Commission of New South Wales, and the University of Newcastle in Australia. Rainfall collection using open and event-activated collectors at 32 sites occurred for 44 events between October 1984 and March 1986, providing the most detailed acid-rain data base available for an Australian region. The structure and organization of the project are described and results of the pH measurements, which indicate volume-weighted pH averages between 4.9 and 5.6, depending on season and type of gauge, are presented-pH values less than 5.0 were measured 37.3 percent of the time in the event-activated rainfall samples. The pH results indicate rainwater acidity in the Hunter Region is similar to that of remote areas of the world.