A study was conducted on the character and significance of highway runoff waters for the Washington Department of Highways and the Federal Highway Administration. This preliminary appraisal of runoff quality consisted of a literature review and critique plus a limited amount of field sampling on SR 520. Although a large amount of information is present in the literature concerning urban runoff, there is very little strictly related to highways and their rights-of-way. Highway runoff is similar to urban area runoff but may be higher in heavy metals and oil. A significant fraction of the heavy metals, oil and nutrients are absorbed to the dust and dirt fractions and then may be removed by sedimentation. Runoff from the lake bridges should have a very insignificant effect on Lake Washington in comparison with the urban runoff to the lake. Recommendations are made for mitigating runoff effects and for conducting an intensive study of highway runoff water quality and its significance.