The Project Stormfury modification theory, its physical basis, and the experiment design are described, and the possible effects of such experiments on tropical cyclone motion, rainfall, wind fields, and storm surge are examined. Studies of natural storm variability, exploratory experiments, sensitivity tests, numerical simulations, and theoretical calculations indicate that experiments conducted according to the Stormfury hypothesis could result in reductions of 10% to 15% in the maximum windspeed and associated damage reductions of 20% to 60%, with no apparent significant and/or detectable effect on storm motion or net rainfall accumulated areawide or at specific locations for a moving storm.