Concentrations of Ca, Cu, Li, Mg, K,Na, and Sr at various points in the Hudson River and one of its tributaries during July 1965, have been measured along with conductivity of the water. Ca, Mg, K, Na, and Sr all show a minimum in concentration about 130 km from the mouth, as does the conductivity. The cleanup process necessary to account for this minimum may sharply reduce contribution of dissolved ions to the ocean. Concentration values in ppm averaged over samples taken from three points upstream from the minimum are as follows: Ca, 24.5; Cu, 0.01; Mg, 6.7; K, 1.2; Na, 15.7; Sr, 0.14. There is a large contribution to these elements from ocean waters at least as far as West Point, N. Y., 90 km from the mouth. Upper limits on the concentration of Cr, Co, Fe, Pb, Li, Mn, Ni, and Rb were established.