A greenhouse study was conducted to investigate the effect of mycorrhiza on wheat (Triticum durum) boron (B) uptake under excessive B concentrations. Three levels of B (0, 3, and 6 mg B litre(-1)) were added to pots with or without mycorrhiza. Plant nutrients were added as Hoagland nutrient solution. In general, additions of B with or without mycorrhiza decreased wheat relative yield and increased shoot and root B concentrations. B concentrations in shoots ranged from 30.8 to 589 mg kg(-1). The highest shoot B concentrations were with the highest B treatments (6 mg B litre(-1)). whereas the lowest concentrations were in the control (0 mg B litre(-1)). Mycorrhiza inoculation significantly improved relative yield of unstressed (control) plants, but those increases in relative yield of B-stressed plants were not significant. In general, mycorrhiza inoculation decreased shoot and root B concentrations and uptake. Wheat growing at high B concentrations (6 and 3 mg B litre(-1)) with or without mycorrhiza showed leaf edge burning and necrosis compared with control treatments. The data suggested that mycorrhiza infection can prevent plants from an excessive concentration and uptake of B although that did not improve plant yield. Further evaluation is needed for the effects of mychorriza inoculation on B toxicity.