One hundred and twenty young adult females took either a placebo or 50 mg thiamine, each day for 2 months. Before and after taking the tablets, mood, memory and reaction times were monitored. An improvement in thiamine status was associated with reports of being more clearheaded, composed and energetic. The taking of thiamine had no influence on memory but reaction times were faster following supplementation. These influences took place in subjects whose thiamine status, according to the traditional criterion, was adequate.