Waterfowl food production, availability, and use in brackish impoundments were studied in South Carolina. Widgeongrass (Ruppia maritima), dwarf spikerush (Eleocharis parvula), and seeds of saltmarsh bulrush (Scirpus robustus) were sampled each month. Standing crop of widgeongrass vegetation declined from 241.11 kg/ ha in August to nearly none in December, due mainly to competition from filamentous algae (Cladophora spp.) Widgeongrass seed production was estimated at 6.16 kg/ ha. Although waterfowl fed intensively on widgeongrass seeds, no depletion was detected, and seeds apparently accumulated from year to year. Standing crop of dwarf spikerush declined from 856.20 kg/ ha in September to 363.46 kg/ ha in February, apparently because of waterfowl use. Saltmarsh bulrush seed production was estimated at 464.60 kg/ ha. Seasonal decrease in availability (from 38.58 kg/ ha in October to 15.78 kg/ ha in February) was attributed mainly to seed deterioration, but waterfowl consumed about 27% of the crop. The 3 species sampled made up 91.2% of the total volume of crop and gizzard contents from 186 ducks and 50 coots (Fu/ica americana). Waterfowl, mainly pintails (Anas acuta), consumed about 34% of the food produced by the 3 plant species studied.