The U.S. Bureau of Mines undertook a basic investigation of collimated abrasive water-jet behavior because a more complete understanding of the fundamental process may lead to further technical advances. Laboratory experiments used 2-mm water-jet nozzles and new entrainment apparatus to analyze collimated abrasive water jets operating under varied conditions. Maximum water pressure was 69 mpa to permit use of conventional hoses with a burst- to-operating-pressure ratio of 4. Nozzle and induction line pressures, abrasive induction rates, and jet reactive thrust forces were recorded for each operating condition. Average jet velocity and power were determined from component mass flow rates and reactive thrust force measurements. Relative velocity and cross- sectional distribution of abrasive particles were determined using impact analysis techniques. Other jet characteristics were determined photographically. Properties of free water jets, collimated water jets, and collimated air-water jets were determined for comparison.