A new process has been described for the preparation of CoA from pantothenic acid (PaA), cysteine, and adenine, adenosine or AMP by yeasts and bacteria. In yeasts, about 70〜80% of added AMP was phosphorylated to ATP but only a small amount of CoA (20〜200μg/ml) was accumulated. PaA, cysteine and ATP, when added to the cell suspension of Brevibacterium ammoniagenes, or PaA, cysteine, and adenine, adenosine or AMP added to its cultures, gave CoA in high yields (2〜5mg/ml). The product was obtained by using Duolite S-30,charcoal, and Dowex 1×2. This method is simple and rapid, and requires no special equipment. The yield of CoA from culture broth was 34% and the purity of CoA was 97%. PaA kinase was purified from cell extracts of Br. ammoniagenes and some properties of the enzyme were investigated. PaA kinase was inhibited by CoA and it was suggested that the enzyme regulated CoA levels in the cells.