On June 12, 1959, the Public Health Service issued PHS Publication No. 663, 'National Water Quality Network Annual Compilation of Data, October 1, 1957-September 30, 1958', a compilation of water quality data representing the information collected during the first year of operation of the National Water Quality Network. This Supplement to the original document is a summary of certain segments of the raw data which appear to need immediate consideration because of their urgency or newness -- such as the more recent measures of water quality - radioactivity, organic chemicals and plankton in surface waters. It is not intended to be an exhaustive analysis of the data or an interpretation of what the data may mean. Computations were made and tabulations were prepared for printing on electronic data processing equipment, thus making easily available many comparisons of monthly and annual parameters. Organic chemicals and plankton are summarized on a 20-river basis, by name of river.