and also the Na+/K+ pump. Results also indicate partial inhibition of the third main pathway involved in sickle cell dehydration, the deoxygenation-induced cation conductance sometimes termed Psickle, independent of an effect on RBC sickling. These findings indicate that aromatic aldehydes may protect sickle cells by two distinct and potentially synergistic mechanisms: by interacting directly with HbS to inhibit polymerisation and also independently of any effect on Hb by reducing cation loss, maintaining RBC hydration and hence reducing the concentration of HbS. The latter effects should be taken into account when designing potential therapeutic members of these compounds.