Two restriction fragments of DNA containing the regulatory feature GTG/CAC were experimentally associated with core histones. The reconstituted DNA-histone complexes consisted of different forms of mononucleosomes. Lambda exonuclease and Fnu4HI were used to probe the structure of each distinct nucleoprotein complex. For each of the DNA fragments, one form of particle was produced that showed preferred placement of the core octamer on the DNA. The GTG/CAC base triplets may play some role in determining the final histone core positions in these reconstitutes.