This subject was explored in a special session entitled “Evapotranspiration Modeling: Its Verification and Use,” held during the 1984 Fall Meeting in San Francisco. The session was conceived by the Committee on the Unsaturated Zone (T. N. Narasimhan, present chairman). The subject matter was divided into three areas: evapotranspiration (ET) considerations, modeling, and remote sensing applications. The abstracts of the nine invited and four contributed presentations appeared in Eos (November 6, 1984, pp. 873–874). The purpose of the session was to explore ways to bridge the gap between small-plot and large-area ET theory, both of which are well enough understood to be described with reasonable models. Many small-area models are tied to causal factors. Many of these factors are not conservative over large areas. This leaves a gap in ET modeling that is difficult to bridge.