From Escherichia coli, DNA-membrane-complexes have been isolated which contain about 40% of the ribosomes, about 95% of the DNA and nearly all of the nascent RNA. The kinetic data on pulse labeled RNA show an average time of turnover of about 60 sec both for nascent messenger- and nascent ribosomal RNA. A proportion of the polysomes with nascent messenger RNA as well as most of the nascent ribosomal RNA is found in association with membranes, as has been shown by subfractionations of the DNA-membrane-complex involving treatment with DNase and desoxycholate. In this early transient stage, ribosomal precursor RNA already acquires some ribosomal proteins, as has been shown by arginine pulse label. Data on partial release of DNA from the DNA-membrane-complex by treatment with extremely low doses of DNase indicate that messenger RNA synthesis occurs in clusters on the DNA.