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 ρ 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 $varepsilon$ ≥ 10-9 Wkg-1 were detected and K ρ was generally less than 10-5 m2s-1. In the profiles obtained near the Hawaiian Ridge, many turbulent patches with $varepsilon$ ≥ 10-9 Wkg-1 were observed, although K ρ was generally of the order of 10-5 m2s-1. Along the Izu-Ogasawara Trough running in parallel with the Izu-Ogasawara Ridge, in contrast, remarkably intense turbulent mixing ($varepsilon$ ~ 10-8 Wkg-1, K ρ = 10-4 ~ 10-3 m2s-1) was common throughout the observed water depth.