We have compared efficacy of photon irradiation vs. treatment with 213Bi-anti-EGFR immunoconjugates in CAL33 HNSCC cells under normoxic and hypoxic conditions in order to prove oxygen-independent cytotoxicity of the α-emitting 213Bi-anti-EGFR-MAb. Here, EGFR is linked to head and neck squamous cell carcinoma.