Boron deficiency causes grain set failure and yield loss in many of the world's wheat growing countries. We suggest growing B efficient genotypes as a means to overcome the problem. This study evaluated international germplasm of bread wheat (Triticum aestivum L.), durum wheat (Triticum durum Dest.), triticale (Triticosecale Wittmack) and barley (Hordeum vulgare L.) for B efficiency. The first set of germplasm consisted of bread wheat, durum wheat and triticale from CIMMYT 1996/1997 nurseries and a B efficient check wheat cv. 'Fang 60'. The lines were grown in the field on soil with 0.1 and 0.2, and 0.3mgHWSBkg-1 for durum wheat and triticale. The grain set index (GSI, percentage grain set in the first two florets of 10 central spikelets) measured B efficiency in wheat, durum and triticale genotypes without the need for a B sufficiency control. Three-quarters of the lines tested were B inefficient, which included all of the durum wheat, 84% of the triticale and 60% of the bread wheat lines. Six of the bread wheat lines evaluated were in the same B efficient class as Fang 60. The response to low B was confirmed in a sand culture experiment without added B. Similarly high frequency of B inefficiency was found in a second set of germplasm which included bread and durum wheat, barley and triticale lines from CIMMYT and ICARDA 2000/2001 international nurseries. Incorporating the B efficiency trait in germplasm such as these, would ensure their adaptation to low B soils, and so enable their genetic potential to be fully realized in some of the world's difficult production areas. © 2003 Elsevier B.V. All rights reserved.