Lactobacillus plantarum was grown in complex media containing glucose and yeast extract. The maximum growth yield based on yeast extract consumption was 0.5 g dwt g-1. Growth yield YATP 15-17 g dwt mol ATP-1 was almost constant in the glucose limited A-stat experiment whereas in the yeast extract limited culture it increased with dilution rate. The maximum specific growth rate observed, 0.5 h-1, was similar for both A-stat and batch cultures. Specific oxygen consumption, QO2, reached the value of 1.8 mmol O2 h-1 g dwt-1. It was shown that Val, Ile, Leu, Tyr and Phe, were consumed mainly as free amino acids, while Asp, Pro, Lys and Arg were derived from peptides. Significantly more Asp, Ser, Glu, Val, Ile, Leu and Phe were consumed than needed to build up cell protein whereas some Pro, Gly, Ala and Lys was synthesized. A network of metabolic reactions in L. plantarum was proposed on the basis of the experimental data.