Analysis of termite attacks on buildings and results of laboratory expt. are in agreement with the reports of others that subterranean termites of the genus Reticulitermes rarely, if ever, construct tubes upward over foundation walls in the open. The cases which we have seen where such activity has occurred have resulted from excessively large colonies developed where there was wood in the ground adjacent to the foundation walls. In dark, confined places such as basementless areas, Reticulitermes may build tubes over foundation walls to reach wood above. The probability or frequency of this activity depends upon such factors as relation of termite population to size of area, wood adjacent to the wall, and ventilation. The majority of tubes seen on foundation walls in the East are constructed downward. Under special conditions termites may reveal unusual types of activity such as travelling for many hrs. without tubes, constructing tubes from both ends, or building up many feet in the open.