The Fanconi genes BRCA2, FANCC and FANCG are mutated in a subset of pancreatic cancer. Additionally, the Fanconi pathway is inactivated, probably by FANCF promoter methylation, in a subset of ovarian cancers. The competence of the proximal Fanconi pathway was screened by an assay of Fancd2 monoubiquitination in a panel of 35 cancer cell lines: 15 breast, 6 prostate, 8 head and neck, 4 biliary cancers, an astrocytoma and a large cell lung carcinoma. Two (6%) cell lines displayed abnormal Fancd2 monoubiquitination: the head and neck cancer cell line FaDu and the breast cancer cell line UACC812. In UACC812, we found that FANCF was not expressed. In the case of FaDu, no explanation for the abnormal Fancd2 monoubiquitination was found. FaDu had a moderately increased sensitivity to mitomycin C, as compared to two Fanconi proficient head and neck cancer cell lines. Future studies should aim to investigate the involvement of defects in the Fanconi pathway in breast and head and neck cancer.