Systematic chemical quality-of-water investigations have been carried on in both Oklahoma and Arkansas by the Geological Survey in cooperation with State and Federal agencies during the past several years. Results of the Survey's quality-of-water investigations are usually published in the annual Water-Supply Papers. However, as the Geological Survey has made no sediment investigations in the Arkansas River Basin in Oklahoma and Arkansas, the published data do not include information on sediment concentrations or loads. This report attempts to summarize information collected to date in the Arkansas River Basin of the two States, and to show as clearly as possible from present information how the chemical quality of water in the Arkansas River changes downstream from the Oklahoma-Kansas State line to its confluence with the Mississippi River, and how it is affected by tributary inflows. Additional information is being collected and further studies are planned. Hence, the conclusions reached herein may be modified by more adequate information at a later date. The Arkansas River enters Oklahoma near Newkirk on the northern boundary just east of the 97th meridian, crosses the State in a general southeasterly direction flowing past Tulsa, enters Arkansas at its western boundary north of the 35th parallel near Fort Smith, still flowing in a general southeasterly direction past Little Rock near the center of the State, and empties into the Mississippi River east of Dumas. The Arkansas River is subject to many types of pollution downstream from the Oklahoma-Kansas State line, and its inferior quality along with an erratic flow pattern has caused it to be largely abandoned as a source of municipal and industrial water supply. At the present time, the Arkansas River is not directly used as a source of public supply in any part of the basin in either Oklahoma or Arkansas. In general, the river water increases in chemical concentration downstream from the Oklahoma-Kansas State line to Tulsa, due mainly to tributary inflow from the Salt Fork Arkansas River and the Cimarron River, both streams being sources of large amounts of both natural and artificial pollution. A decrease in chemical concentration is noted downstream from Tulsa due to tributary inflow from the Verdigris, Neosho, and Illinois rivers with an increase in chemical concentration then noted due to tributary inflow from the Canadian River which is largely artificial pollution. A steady decrease in concentration is then noted as the river progresses through Arkansas to the Mississippi River, as all major tributaries below the Canadian River have a dilution effect upon the chemical concentration of the Arkansas River water. Proposals for storage and regulating reservoirs on the Arkansas River in both Oklahoma and Arkansas have been made by the Corps of Engineers and others. Additional proposals are being considered in the present Arkansas-White-Red River Basin Inter-Agency Committee studies. If constructed, these reservoirs will provide an opportunity for control of flow and beneficial use of Arkansas River water, both at and downstream from these sites. Impoundment alone will greatly reduce the extremes in water quality, and by reasonable control of municipal and industrial wastes, the water would be comparable in quality to many existing basin municipal and industrial supplies. (available as photostat copy only)