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[1] Microstructure measurements from the surface down to maximum depths of $2000 m were carried out at 28 locations in the interior of the North Pacific. Special attention was directed to the diapycnal diffusivities K r in the significant generation regions of the semidiurnal internal tide such as the Aleutian Ridge, the Hawaiian Ridge, and the Izu-Ogasawara Ridge. In the profiles obtained near the Aleutian Ridge, only a few turbulent patches with e ! 10 À9 Wkg À1 were detected and K r was generally less than 10 À5 m 2 s À1 . In the profiles obtained near the Hawaiian Ridge, many turbulent patches with e ! 10 À9 Wkg À1 were observed, although K r was generally of the order of 10 À5 m 2 s À1 . Along the Izu-Ogasawara Trough running in parallel with the Izu-Ogasawara Ridge, in contrast, remarkably intense turbulent mixing (e $ 10 À8 Wkg À1 , K r = 10 À4 $ 10 À3 m 2 s À1 ) was common throughout the observed water depth.