The effect of sodium dodecyl sulphate on the flotation of Al2O3 from samples of gibbsite of Sinai (Egypt) shale was studied at various operating variables. The assays of the samples are 18·98%Al2O3, 15·45%SiO2, 12·83%Fe2O3, 14·87%CaO, 5·74%P2O5, 5·34%MnO, 0·86%K2O, 0·76%Na2O, 1·50% trace elements and 23·65% loss on ignition. The aim of upgrading Al2O3 per cent in the concentrate is to make it suitable for different industrial uses. Sodium dodecyl sulphate (anionic collector) is effective in the acidic pH range. Below the zero charge point of gibbsite where Al2O3 is positively charged, the sodium dodecyl sulphate is good at pH 2. Under appropriate conditions [collector dosage, 800 g t−1; pulp density, 300 g L−1; particle size, (−100+80) μm and pH 2], a concentrate containing 39·5%Al2O3 at component recovery of 96·9% with mass recovery of 52·8% was obtained. At these conditions, the assays of other ore constituents in the final concentrate were as follows: SiO2 decreased from 14·2 to 6·4%, CaO decreased from 14·1 to 5·2%, Fe2O3 decreased from 13·1 to 5·6%, P2O5 decreased from 4·3 to 3·8%, MnO decreased from 4·2 to 3·2%, while K2O increased from 0·89 to 1·2%, Na2O increased from 0·69 to 1·1%, traces increased from 1·6 to 2·6% and loss on ignition increased from 25·4 to 31·2%.