Protoplasts from barley (Hordeum vulgare), pea (fisum sativum), wheat (Trificum aesfivum), and spinach (Spinacia oleracea) leaves were fradionated into chloroplast-and mitochondrionenriched fractions. Pyruvate dehydrogenase complex capacities in mitochondria (mtPDC) and chloroplasts (cpPDC) were measured in appropriate fractions under conditions optimal for each isozyme. The total cellular capacity of PDC was similar in barley and pea but about 50% lower in wheat and spinach. In pea a distribution of 87% mtPDC and 13% cpPDC was found on a cellular basis. In barley, wheat, and spinach the subcellular distribution was the opposite, with about 15% mtPDC and 85% cpPDC. cpPDC adivity was constant at about 0