1. 3-Deoxy-D-arabinoheptulosonate-7-phosphate synthetase(phe) from Escherichia coli K12 has been purified to near homogeneity. The purified enzyme has a specific activity of 67 units/mg which is about 1000 times that found in cell-free extracts of wild-tupe E. coli K12. 2. The minimum molecular weight of the enzyme was estimated by dodecylsuphate-gel electrophoresis to be 33000. Re-estimation of the native molecular weight by gel filtration confirmed the previously determined value of 110000. 3. Amino acid anaktsus abd tryptic fingerprints indicated that the subunits of the enzyme are very similar and possibly identical. 4. The purified enzyme does not contain Co2+.