The Hayatomo Strait is located on one of the most important maritime routes in Japan. The trend of increase in the vessels passing its narrow and curved fairway with strong tide made us feeling the necessity of the present survey. Three series of 24 hour radar photographic and visual observations were conducted on Aug.17, 21, and 26, 1966, after a preliminary observation on Aug.14. And the results obtained are summarized as follows: 1. As many as 900 vessels passed through the strait a day. 2. About 60% of them were those smaller than 100 G.T. 3. About 70% of them passed in the daytime and the rest at night, the rush hour being from 06.00 to 10.00. 4. The strong tidal current did not cause any remarkable decrease in passing of the vessels. 5. The course of passing varied with the size of vessels: Those over 1, 000 G.T. were inclined to pass along the fairway regardless of the relative direction and the speed of the tidal current. Most of the boats of not larger than 100 G.T. were inclined to take the course very close to the southern coast especially when they pass against the current, but to take diverse courses over, the fairway when they pass follwing the current.