The case for the retention of uneconomic forests against other land use pressures has often been based. in East Africa. on the beneficial influences of forests on the hydrological regime. A brief review is given of the influences of forests on climate, soil moisture and streamflow, presented in the light of results from catchment area experiments in East Africa. Stress is laid on the conditions when the above case is likely to be valid and of more than marginal significance. In East Africa, where surface storage opportunities are small, rational catchment management must aim at maintaining the maximum infiltration rate, but the transpiration loss by tropical evergreen forest is likely to be high and any hydrological arguments for forests in regions with an annual rainfall of less than 50 in. must be reviewed very carefully. Finally, an outline of suitable land uses in varying circumstances is tentatively presented for general guidance in the absence of more detailed information.