Results are presented of a 2-year study involving the identification and assembly of a data base existing within the Publicly Owned Treatment Works (POTW) of the U.S. on influent heavy metals. The general character of the data base with respect to associated descriptors (among which are % industrial contribution, % combined sewers, % infiltration/inflow, sample frequency, sample type, analytical method) is provided. Wastewater treatment plant laboratories were evaluated in the conduct of the study and generally found to be satisfactory within the framework of the evaluation method. Of the 80,000 individual pieces of data from 239 wastewater treatment plants, a substantial data base was generated for cadmium, copper, nickel, lead and zinc. Extensive data (but reduced in total volume) were obtained for silver, arsenic and mercury. Limited data were obtained for beryllium, cobalt, antimony and selenium. Aluminum, iron and manganese data were received as well. Median and mean (computed in varying manner) are reported and compared. Generally, log normal distributions were observed for all but the data extremes. While no associations could be demonstrated between the median or mean values for the composite data base and the individual descriptors using Pearson and Spearman techniques, isolation of the low percent industrial waste category from the parent data base did show significant differences for 6 of 7 metals. Lead was the metal not showing a difference.