AIMS: To survey the expression of members of the S100 family of calcium-binding proteins in normal human tissues and common cancers using tissue microarrays. S100A6, S100A8, S100A9 and S100A11 have all been suggested to have potential roles in carcinogenesis and tumour progression but their expression has not been described in a wide range of human tissues and tumours. METHODS AND RESULTS: A custom-made tissue array, containing 291 tissue cores representing 28 tissue types and 21 tumour types, was used to produce sections that were immunostained for S100A2, S100A6, S100A8, S100A9, S100A11, calbindin 1, calbindin 2, S100B and parvalbumin. S100A6, S100A8 and S100A9 were expressed in 32%, 12% and 28% of breast cancers, respectively. There was a translocation of S100A11 expression from exclusively nuclear in normal tissues to cytoplasmic and nuclear in all common cancers. CONCLUSIONS: S100A6, S100A8, S100A9 and S100A11 are all expressed in common cancers, especially breast cancer. In addition, S100A11 undergoes a nucleocytoplasmic translocation which may have a direct influence on the proliferation of the cancer cells.