The role of aluminum accumulation in articular tissues of patients affected by dialysis-associated arthropathy (DAA) is questioned. The aim of this work is to identify the nature of these aluminum accumulations by the use of secondary ion mass spectrometry (SIMS). Al/Si ratios of about 1, measured by SIMS, strongly suggest for the first time the presence of aluminum silicates and possibly aluminum hydroxides in amyloid synovial tissue and articular cartilage of 1 patient with DAA and aluminum intoxication. This is thermodynamically consistent with the total dissolved Al and Si contents and pH measured in the synovial fluids. These results are similar to the abnormal Al distribution recently found by SIMS in the forebrain of chronic renal dialysis patients and to the amorphous aluminum silicates identified in the core of senile plaques in Alzheimer's disease.