1. The phenomenon of entangled fermentation previously found and expressed as follows:glucose+2 pyruvate→2 lactate+2 CO2+acetoinwas reinvestigated in L. plantarum, and the above equation was confirmed.2. Entangled fermentation was further studied by tracer techniques. All of the fermentation products, lactate, CO2, and acetoin were found to derive one half of their carbon atoms from glucose and the other half from pyruvate.3. Periodate degradation of the acetoin molecule showed that the acetyl moiety of the molecule originates from pyruvate and the methyl carbinol moiety from glucose.