The stability of the sonic point in an isothermal accretion disc is examined for the case in which a new revised viscosity is adopted. From this viscosity, it follows that at a sonic point T
r
Φ = − 2vΣΩ/(l + 2C
s
τ/r). The results show that the sonic point is a saddle and stable against small amplitude perturbations. Finally, we discuss these results.
