Rooted aquatic plants in the Upper Potomac Basin are not a significant factor in the nutrient budget of the lower Potomac River. In August 1969 the standing crop of rooted aquatic plants in the Upper Potomac River Basin contained 400 pounds of phosphorus and 4400 pounds of nitrogen. These quantities are equivalent to approximately 40 percent of the phosphorus and nitrogen in wastewaters discharged to the Upper Potomac River in a single day. Standing crop estimates were made for growths in Antietam Creek, Conococheague Creek and the Potomac River. Other basin streams contained too few growths of rooted plants to merit sampling for standing crop estimates.