The effect of hemodialysis (HD) on olfactory recognition and memory function was investigated in people receiving chronic HD treatment. Fifteen subjects were given an olfactory recognition task 0.5 h before and 0.5 h after a dialysis session in counterbalanced order. Ten dialysis patients received a verbal recall task twice. Ten age-matched normal subjects received the olfactory task twice. Results were: (1) olfactory scores in the HD group were significantly lower than control subjects scores; (2) within the dialysis sample, olfactory identification scores were significantly lower after treatment than before, and (3) there were no parallel decreases in memory performance of the dialysis group after a HD treatment. We therefore conclude that those subjects receiving HD treatment demonstrate acute and chronic deficits in olfactory recognition which are unlikely to be due to fatigue, cognitive disequilibrium, anticoagulant treatment or high levels of uremic toxins.