Thiamine deficiency can have cardiovascular and neurological manifestations. Cardiac beriberi is classically thought to represent a high-output state with oliguria and lactic acidosis. The condition can, however, also present itself with a low cardiac output and fulminant vascular collapse, or as an acute fatal form, causing sudden death, without clear-cut signs of cardiomegaly. In the western society beriberi is mainly encountered in alcoholics. We report on two cases, one with high-output failure and the other with low-output failure and cardiovascular collapse. In both patients the diagnosis of shoshin syndrome was made, and and both showed a spectacular improvement of congestive heart failure symptoms after treatment with thiamine. A therapeutic trial with thiamine is the only way to rapid diagnosis.