We describe different methods of electrothermal atomic absorption spectrometry with automatic sampling for determining aluminum in human serum, blood, urine, and tissues. Contamination with Al originating from receptacles and reagents was minimized. Whole-blood Al concentrations were measured after hemolysis of EDTA-anticoagulated blood samples with Triton X-100. A straightforward method for tissue destruction was developed. Instrument settings of the graphite furnace and of the atomic absorption spectrometer were adjusted so as to obtain close agreement between direct and standard-additions methodologies. The result is a reliable direct method appropriate for use with multiple samples. Tissue Al measurements showed low detection limits and approximately 100% analytical recoveries. Al concentration in serum of 10 healthy volunteers and of 100 chronic hemodialysis patients were 2.0 (SD 0.4) and 77 (SD 70) micrograms/L, respectively. Blood Al concentrations of 10 controls and of 100 dialysis patients were 12.1 (SD 1.5) and 79 (SD 70) micrograms/L, respectively. Al concentrations in serum and blood of 47 chronic hemodialysis patients were not significantly different. Bone Al concentrations were 8.2 (SD 5.8) micrograms/g of fresh tissue for 10 chronic hemodialysis patients without osteomalacia, as compared with 51 (SD 20) micrograms/g for 10 chronic-dialysis patients with Al-induced osteomalacia.