A 16 week study of leaf decomposition for sweetgum (Liquid-ambar styraciflua), American sycamore (Platanus occidentalis), and baldcypress (Taxodium distichum) was conducted during winter 1983–1984 in thermal and non-thermal streams and floodplain swamps in South Carolina. Mean daily temperatures ranged from 7.6 to 49.0 C in streams and from 10.5 to 29.8 C in swamps. Sweetgum leaves consistently decomposed more rapidly than sycamore leaves and leaf decomposition rates for sweetgum and sycamore tended to be inversely related to thermal regimes. Cypress leaves showed relatively uniform, slow losses over all temperature ranges. The highest processing rates for all leaf types were found in non-thermal, closed-canopy swamp habitat, where the shredding caddisfly, Pycnopsyche sp., was relatively abundant.