Two models of interception loss have been tested against new field data obtained in widely-spaced stands of Sitka spruce trees. The Gash model and a modified version of the Rutter model, have been used with data from an automatic weather station, to predict interception loss using parameters obtained from observations made in 1988 and 1989. The predictions for an eight-week period during 1987 were compared with measurements of interception loss. Good agreement between observed and predicted interception loss was obtained with both models over the whole period. The modified Rutter model gave better predictions than the Gash model for individual storm events and performed better at the wider spacings. The sensitivity of both models to the major characteristics of the tree stand structure in agroforestry systems was also investigated and it was shown that interception loss was most sensitive to boundary layer conductance and free throughfall coefficient.