This paper investigates the possibility that interstellar turbulence is caused by nonlinear interactions among shear Alfvén waves, focusing on the symmetric case where oppositely directed waves carry equal energy fluxes. The authors derive a kinetic equation for strong shear Alfvénic turbulence, which exhibits a critical balance between linear wave periods and nonlinear turnover timescales. The eddies are elongated along the direction of the magnetic field, with an aspect ratio of \( k_z \approx k_{\perp}^{1/3} L^{-1/3} \). The energy spectrum is anisotropic, proportional to \( k_{\perp}^{2/3} \). Shear Alfvénic turbulence mixes specific entropy, leading to electron density fluctuations that mimic the turbulence's energy spectrum. Radio-wave scattering by these fluctuations produces anisotropic images. Damping by ion-neutral collisions restricts turbulence to highly ionized regions. The authors conclude that the critical balance theory supports the general picture of interstellar turbulence advanced by Higdon.This paper investigates the possibility that interstellar turbulence is caused by nonlinear interactions among shear Alfvén waves, focusing on the symmetric case where oppositely directed waves carry equal energy fluxes. The authors derive a kinetic equation for strong shear Alfvénic turbulence, which exhibits a critical balance between linear wave periods and nonlinear turnover timescales. The eddies are elongated along the direction of the magnetic field, with an aspect ratio of \( k_z \approx k_{\perp}^{1/3} L^{-1/3} \). The energy spectrum is anisotropic, proportional to \( k_{\perp}^{2/3} \). Shear Alfvénic turbulence mixes specific entropy, leading to electron density fluctuations that mimic the turbulence's energy spectrum. Radio-wave scattering by these fluctuations produces anisotropic images. Damping by ion-neutral collisions restricts turbulence to highly ionized regions. The authors conclude that the critical balance theory supports the general picture of interstellar turbulence advanced by Higdon.