Fourteen individuals on long term hemodialysis, with varying amounts of aluminum in bone from 11 to 296 mg/kg by flameless atomic absorption spectrophotometry, were examined to see whether the aluminon or acid solochrome azurine (ASA) staining reactions best approximated the chemical determination. Correlation coefficients were 0.78 for aluminon and 0.88 for ASA. Together with 11 additional patients morphometric parameters were compared with the two aluminum stains. The aluminon stain gave satisfactory results in the osteomalacic group but underestimated the amount of aluminum present in those with hyperparathyroid, mixed or aplastic disease. Some individuals showed a striking difference between the two techniques which could have led to an erroneous conclusion regarding the amount of aluminum present. The aluminon stain was pH dependent and together with ASA could be enhanced by prior heat treatment of the sections. It is recommended that ASA either replace aluminon for routine use or be used together with the aluminon stain, particularly for bones without osteomalacia or with mild to moderate aluminum storage.