We have obtained direct measurements of diffuse hydrothermal effluent temperature, velocity and chemistry from the TAG hydrothermal mound, 26¿8'N, 44¿49'W, Mid-Atlantic Ridge. We report on the time series physical measurements obtained from a location on the eastern flank of the main summit complex. Several features were observed including strong tidal variability in flow, a conspicuous elevation of effluent temperatures during the period 11 October--17 October 1994, and a long term increase in temperature superimposed upon all other trends. The six-day-long temperature excursion is coincident with increases in sediment and effluent temperatures observed by instruments left in place on the TAG mound by other workers. We have established through time-lapse seafloor video observations and through drilling records that the mid-October effluent temperature excursion is correlated closely with local drilling activity by the Ocean Drilling Program. ¿ American Geophysical Union 1996