Diseases due to vitamin B1 (thiamin) deficiency are considered to be uncommon in Israel. We present 13 patients admitted during the course of a year who were found to have thiamin deficiency. 5 had classic syndromes such as beri-beri, Wernicke's encephalopathy and cerebellar degeneration. In another 8 the thiamin deficiency was found during workup for less specific neurological abnormalities. Only a minority were alcoholics. Mainly at risk for developing nutritional deficiency were the solitary elderly of low socio-economic status with poor nutrition. Other reasons for thiamin deficiency were drug abuse and hyperemesis gravidarum. Thiamin levels should be determined not only in alcoholics and those with classic B1 deficiency syndromes, but in the routine workup of patients with sensory-motor neuropathy, dementia, gait disorders, cerebellar syndromes and confusional states. It is advised to give vitamins prophylactically to asymptomatic high risk patients.