Water samples taken at seven locations along the length of the Ottawa River in July, 1972, have been analyzed for 35 elements using thermal neutron activation and high resolution Ge(Li) detectors. Despite major sources of pollution on the river most macrocomponents (> 1 μg/l) are relatively unaffected. An anomalous decrease in concentration is found at one of the sampling stations for elements < 1 μg/l. Abnormal fractionation of most elements between water and suspended material was observed in a section of the river where large quantities of fresh wood fibres were being produced by a fluming operation.