Digestibility studies conducted with South American camelids on conserved forages have identified lower intakes and higher digestion coefficients in comparison with sheep when fed low and medium quality diets (Hintz, Schryver and Halbert, 1973; San Martin and Bryant, 1989). However, such experiments often involve only one or two animals. There are no published reports of detailed comparative in vivo trials based on fresh forage. The aim of this study was to compare the voluntary intake and digestion coefficients of guanacos and sheep when zero-grazed on a comparatively high quality ryegrass sward at three different growth stages.