Adobe samples from historic structures in Arizona were analyzed to determine their mineral assemblages, particle size distributions, soluble salt contents, and porosities. Microscopic observations of polished sections and thin sections were also performed. These data were correlated with the weathering observed. Soluble salt action was primarily responsible for the deterioration of the adobe from one site. The nature of the particle size distribution contributed to the rapid deterioration of the adobe from a second site. The adobe from a third site was well consolidated due to the presence of large amounts of calcite.