In the present study, NaSi-1 sulphate transporter knock-out (Nas1-/-) mice, an animal model of hyposulphataemia, were examined for spatial memory and learning in a Morris water maze, and for olfactory function in a cookie test. The Nas1-/- mice displayed significantly (P<0.05) increased latencies to find an escape platform in the reversal learning trials at 2 days but not 1 day after the last acquisition trial in a Morris water maze test, suggesting that Nas1-/- mice may have proactive memory interference. While the wild-type (Nas1+/+) mice showed a significant (P<0.02) decrease in time to locate a hidden food reward over four trials after overnight fasting, Nas1-/- mice did not change their performance, resulting in significantly (P<0.05) higher latencies when compared to their Nas1+/+ littermates. There were no significant differences between Nas1-/- and Nas1+/+ mice in the cookie test after moderate food deprivation. In addition, both Nas1-/- and Nas1+/+ mice displayed similar escape latencies in the acquisition phase of the Morris water maze test, suggesting that learning, motivation, vision and motor skills required for the task may not be affected in Nas1-/- mice. This is the first study to demonstrate an impairment in memory and olfactory performance in the hyposulphataemic Nas1-/- mouse.