In this paper, vibrations and acoustic emissions (AEs) of defective linear-guideway type recirculating ball bearings under grease lubrication were measured. The experimental results show that the vibration and AE amplitudes (the pulse amplitudes, the RMS values) of both the normal and defective bearings have a tendency to be reduced when a grease with higher base oil viscosity is used. Under the same type of grease, the RMS values of the vibrations and AE of the defective bearings increase as the defect angle increases. However, the increases of the RMS values due to increased defect angle are reduced when a grease with higher base oil viscosity is used.