1. In most rat liver cells, no special topographical relationship between mitochondria and ergastoplasmic lamellae is to be observed. In some cells, nevertheless, the two organelles are grouped together in dense zones clearly separated from the hyaloplasm. 2. Such an association can be produced at will in the livers of animals refed after prolonged fasting, or in the regenerative phases after partial hepatectomy and intoxication with carbon tetrachloride. In all these cells, the ergastoplasm, after having disappeared, suddenly reappears in the cytoplasm, either along the nucleus or cell membranes, where the mitochondria are grouped. 3. It may be supposed that these topographical relationships between mitochondria and ergastoplasm during a definite period of cellular activity indicate a close functional link between chondrioma and basophilic structures. Mitochondria seem to play an important part in the elaboration of hepatic ergastoplasm.