Aluminum toxicity is frequently the limiting factor to crop production in acid soils. The diagnosis of AI toxicity for a specific wheat (Triticum aestivum L.) cultivar could be simplified by tissue analysis.Greenhouse studies were undertaken to determine the critical AI toxicity level for the cultivar 'Stacy' and tissue nutrients affected by AI status. Wheat plants were grown in 10 levels of AI (0, 1.9, 3.7, 9.3, 18.5, 37.1, 74.1, 148, 222, and 297 JJ.M AI) in nutrient solution for 28 days. Aluminum toxicity reduced top dry weight, root dry weight, plant height, tiller numbers, and top/root dry weight ratio. Aluminum concentrations in the blade and stem tissues were low (maximum of0.3 mmol kg-1 in Blade I, the most recently developed leaf with a developed ligule) and were linearly related to AI in nutrient solution. Aluminum is not readily accumulated in Stacy wheat. The critical AI toxicity levels, defined as the AI concentration in the tissue associated with a 10% decrease from maximum top dry weight due to toxicity, were 0.12 mmol kg-1 in Blade I and 0.08 mmol kg-1 in the whole plant. Knowing these tissue values, one may be able to detect AI toxicity from similar uncontaminated tissue from the Stacy cultivar sampled in the field. Using washed Blade I would be preferable to using the whole plant because soil contamination would be minimized. Aluminum toxicity decreased all elemental concentrations in Blade I and whole plants. With the exception of P and K in Blade I, the decreases in elemental concentrations were related by either a linear or quadratic regression.