The coupling between ion oscillations and electric currents introduced by collisional effects was studied. A growth of ion acoustic waves is found which extrapolates to the Vlasov gas value as the collision mean free path and wavelength become comparable. The damping of ion acoustic waves is calculated from the fluid equations. For a plasma confined by a strong magnetic field, convective oscillations can be excited by an electron drift along the magnetic field lines. The growth rate and frequency of these oscillations is compared to stellarator experiments.