The effects of the inclusion of increasing quantities of cereal straw treated with sodium hydroxide in the diet of rabbits weie studied on 68 animals, both males and females, of the Spanish Giant and New Zealand × Spanish Giant breeds, weaned at different weights. The nitrogen and fibre digestibilities, the overall growth rate (from weaning to 2·25 kg) and the partial growth rate (from weaning to 2 weeks after weaning) increased linearly, while the feed conversion rate decreased when the content of treated straw in the feed was raised. The overall growth rate for males was significantly higher (P < 0·001) and feed conversion rate lower (P < 0·01) than for females. The crossbred animals had a significantly higher overall (P < 0·001) and partial (P < 0·05) growth rate. As weaning weight increased, overall (P < 0·001) and partial (P < 0·05) growth rate also increased, whereas the dressing percentage of the carcass decreased significantly (P < 0·01).