The sole, normally a demersal fish, occasionally migrates to the surface especially in the period preceding the spawning season in spring. This phenomenon was studied by means of verbal inquiries among Dutch fishermen in the springs of 1963, 1964 and 1965. From a total of 2,500 interviews 441 positive reports revealed that swimming at the surface results in a speedy migration from deeper water to the spawning grounds near the coasts of Holland, Germany and Denmark. Soles only migrated to the surface during the night and only when the tidal streams were flowing to the NE, E, SE or S guaranteeing transport in a favourable direction. Quick transport was secured by swimming to the surface since maximum current velocity may be expected there. At the surface soles, lying nearly immobile, normally were heading NE and E even when they were carried in other directions by the tidal streams. This suggests that two types of orientation are used, namely selection of the appropriate tidal current direction before reaking surface and, after having arrived at the surface, an orientation of the body independant of the tidal currents. A number of possible orientation mechanisms are discussed. The concept of compass orientation seems to be most appropriate. Supporting this is the fact that in a number of observations in a restricted area there emerged a distinct relation between the degree of cloud cover and the degree of orientation towards tidal streams, suggesting that celestial cues may be used in the orientation. It appeared that the moon had no influence in this respect.