Stemflow has distinguishable effects on the hydrology and biogeochemistry of wooded ecosystems. Nonetheless, it is a relatively poorly understood hydrologic process. No known studies have investigated the temporal variability of stemflow volume at 5-min intervals in a beech-yellow poplar forest of eastern North America. The aim of this research is to compare the temporal variability of stemflow generation by Fagus grandifolia Ehrh. (American beech) and Liriodendron tulipifera L. (yellow poplar) in relation to tree species and size. Employing a dense network of tipping-bucket stemflow gages interfaced with a datalogger, a 5 min stemflow yield database was assembled and analyzed to better discern how stemflow production varies (temporally) with tree species and size. Results indicate that both tree species and size have detectable effects on the temporal variability of stemflow yield. Observational data, scientific analysis, and correspondence analysis reveals that stemflow yield: (1) is more similar within than between the two tree species with differences likely being attributable to differences in bark texture and water storage capacity; (2) tree size affects stemflow yield within species; (3) rain event characteristics affect stemflow yield; and (4) stemflow yield for particular trees and rain events is the result of a complex set of interactions among tree species, tree size, and meteorological conditions. These results suggest that the temporal variation in stemflow yield from co-occurring forest trees may play a significant role in subsurface drainage of wooded ecosystems during rain events.