In addition to our finding that intravenous SOD administration immediately after photodynamic light treatment decreases the cure rate of PDT-treated mouse FsaR and EMT6 tumours (Korbelik et al, 2000), Athar et al (1989) have shown that the effect of PDT on mouse skin can be augmented by an SOD inhibitor and diminished by an SOD mimic. Here, SOD1 is linked to neoplasm.