Rangelands, though marginal for arable agriculture, are an important agricultural resource in many countries. They also represent a particular challenge for extension services: there are conflicts of interest between different categories of user, and agricultural research does not yet give many definitive technical points of intervention. Common interpretations of extension such as ‘technology transfer’ to individual farming families are inadequate in these circumstances, as the case of the Yemen Arab Republic illustrates. A wider understanding of extension is needed, one which recognizes the variations in, and adaptability of, local farming systems. Basic principles of good land and livestock husbandry can be taught; communities and individuals who have proved more successful than others can be identified and their practices tested, refined and made more widely known; and extension workers can play an important part in the search for suitable institutional arrangements for the management of communally held resources.