Abstract –A method is presented by which rat facial processes from different stages were obtained in pure fraction. The morphology, and protein and DNA contents in free dissected facial processes were determined. Facial processes of embryonic rats aged 9‐15 days were analyzed by isoelectric focusing for their isoenzymic distribution of four enzymes: lactate dehydrogcnase, creatine phosphokinase, fructose diphosphate aldolase and phosphoglycerate mutase. A dominance of LDH‐5, LDH‐4 and LDH‐3 isoenzymes was observed. As a comparison, LDH isoenzymes from mandibular and maxillary processes of rat embryos aged 9‐11 days only revealed LDH‐5 and to a smaller extent LDH‐4. The results support the presence of a prominent anaerobic metabolism in these tissues during early facial development. The change to LDH‐3 development correlates well with the formation of new blood vessels. From the ninth embryonic day, isoenzyme BB of creatine phosphokinase was present and during days 10‐15 MB and MM developed. Isoenzyme As4of fructose diphosphate aldolase was present from the ninth embryonic day and isoenzymes A3C and A2C2developed during days 10‐15. From the tenth embryonic day, isoenzyme BB of phosphoglycerate mutase was present and during days 10‐15 isoenzyme MB and MM developed. Isoenzyme development was first seen in mandibular processes, followed by maxillary, lateral nasal and medial nasal processes, and it preceded morphologic evidence of sk