The role of linker histones in the assembly of functional nuclei was examined with the use of a cell-free extract of Xenopus eggs that transforms condensed sperm chromatin into DNA-replication-competent pronuclei. When linker histones were removed from the extract, the resultant pronuclei were indistinguishable from those formed in the complete extract. The assembly of functional nuclear membrane, nuclear lamina, and prereplication centers allowed identical DNA replication efficiencies. Thus, linker histones are not required for the assembly of morphologically normal nuclei capable of DNA replication.