Maximum winds in Hurricane Debbie, August 1969, decreased after modification experiments by Project Stormfury. Clouds surrounding the center of Debbie were seeded with silver iodide particles five times at approximately 2-hour intervals on both 18 and 20 August. Before the first seeding on 18 August, the maximum speed of winds at 3600 meters was 182 kilometers per hour, but, 5 hours after the fifth seeding, these winds decreased to 126 kilometers per hour. On 20 August, the corresponding change was from 183 to 156 kilometers per hour. Analyses of the data suggest that the storm was modified.