The suspended loads at three stations in the middle estuary of the River Tay have been analysed monthly, at low and high water of the spring tides, over the period June 1983 to May 1984. Major mineral modal analyses were derived from bulk and mineral oxide analyses. The concentrations in the suspended loads of the trace metals Cr, Cu, Pb and Zn were determined. An efficient circulatory system operates within the middle estuary which largely retains the suspended loads acquired from the inner estuary, even at seasonal periods of high influx. The major mineral assemblage is quartz, chlorite, illite and kaolinite. There is some preferential landward return of quartz and chlorite. Chromium has an association with chlorite, while copper, lead and zinc seem linked with suspended particulate organic matter which, at least in part, is derived from sewage disposal into the estuary. Dissolved zinc is associated with dissolved organic matter.