The results from many experiments conducted over 5 years to determine the tolerance of 34 plant species (87 cultivars) to aluminium (A1) are summarised. All experiments were conducted in a temperature-controlled glasshouse using a low-ionic-strength solution culture technique. The activity of A13+ (/zM) at which top yields were reduced by 50% (A1RYS0) was determined for each cultivar.The species Bromus wildenowii, Cynosurus cristatus, Hordeum vulgare, Triticum aestivum (cvs Warigal, Scout, Sonora-63), Avena byzantina, Arabidopsis thaliana, Lycopersicon esculentum and Nicotiana plumbaginifolia were all very sensitive to AI (AIRvs0 < 1). The species Poa pratense, Lolium perenne (NZ-derived cultivars), Lotus corniculatus, Avena sativa (cvs West, Carbeen, Camellia and Coolabah), Triticum aestivum (cvs Cardinal and Waalt), Allium cepa and Asparagus officinalis were sensitive to A1 (AIRv5O 1-2).The pasture grass species Lolium perenne (Australian and European and derived cultivars), Lolium hybridum and Lolium multiflorum, Dactylis glomerata (Apanui and Kara), Phalaris aquatica, Festuca arundinacea and the pasture legumes species Trifoliurn pratense, Trifolium repens and Trifolium subterraneum were all moderately sensitive to AI (A1Ry50 2-5). Other species that were also moderately sensitive included Triticum aestivum (cvs Atlas-66, BH146, and Carazinho), Arena sativa (cvs Swan and Blackbutt), Avena Strigosa, Petunia x and Phaseolus vulgaris (cvs Red Kidney, Black Turtle and Haricot).The most tolerant species (AIRyso > 5) were (in order of increasing tolerance) Phaseolus vulgaris (cvs Tendergreen, The Prince and Yatescrop), Cucurbita maxima, Dactylis glomerata (cv Wana), Paspalum dilatatum, Lotus pedunculatus, Ehrharta calycina, Medicago sativa, Holcus lanatus, Festuca rubra, Phaseolus lunatus and Agrostis tenuis. Agrostis tenuis was at least twice as tolerant as the next most tolerant species (A1RvSO > 30 compared to 15.6).