Many different population groups throughout the world have thiamine deficiency and are at risk of developing severe neurological and cardiac disorders. Alcoholics are most at risk but other important clinical groups should be monitored carefully. The most severe, potentially fatal disease caused by thiamine deficiency is the neurological disorder Wernicke–Korsakoff syndrome. This can be difficult to diagnose and many cases remain undiagnosed. Treatment with thiamine generally results in a dramatic clinical improvement. Thiamine supplementation of stable food products like flour is an effective, simple and safe public health measure that can improve the thiamine status of all population groups.