Calcium distributions on internal and external surfaces of longitudinally sectioned hairs were analysed with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS). Externally, calcium deposits were observed at the cuticle scale edges. Internal sections showed that the bulk of calcium exists within or just inside the cuticle layer. The medulla may or may not be enriched and other localised concentrations exist in one of two forms; either associated with granular structures or the hair proteins. Calcium appears to show an affinity for proteins with low sulfur content.