Autohydrolysis of sunflower seed hulls at 200°C for 5 min followed by explosive defibration solubilized >80% of the total hemicellulose (heteroxylan) and 85% of the pectic substances. The remaining residue, which consisted of cellulose (38%), lignin (45%) and residual heteroxylan (7%), was highly susceptible to hydrolysis by cellulases (Trichoderma reesei C-30, Meicelase and Onozuka 3S). Enzymic digests containing 10% (w/v) substrate and 20 FPU/g pretreated hull resulted in sugar yields of >40% within 24h. This yield was increased toca. 70% when digests were supplemented with exogenous β-glucosidase. The method has potential use in the bioconversion of sunflower seed hulls into chemicals.