Red blood cell transketolase activity, before and after addition of thiamine pyrophosphate, was the same in 17 cirrhotic patients and in 31 normal volunteers and chronically ill noncirrhotic patients receiving an adequate thiamine intake. Blood lactate and pyruvate levels and L/P ratios were higher in the cirrhotics. Thiamine supplementation did not alter these results. PaO₂ was lower in the cirrhotic group. pHa and PaCO₂ were not different from controls. Although thiamine dependent enzymes were not evaluated in ether tissues, the red blood cell data suggest that these patients can utilize thiamine normally. Factors other than thiamine deficiency (circulatory changes, hyperventilation, cellular damage) may explain the alteration in lactate-pyruvate metabolism observed in these patients.