The low-frequency noise behaviour in forward operation of high-energy electron irradiated Si n(+)p diodes is reported. For diodes fabricated on Czochralski substrates, negligible change in noise is observed, whereas for float-zone diodes, a reduction occurs after the irradiation. By comparison with reverse bias gated diode characteristics, it is concluded that the excess 1/f noise of the irradiated diodes is not correlated with the irradiation-induced degradation of the Si-SiO2 interface.