The DNA extracted from human leukemic leucocytes has been fractionated on a methylated albumin kieselguhr (MAK) column. The different fractions obtained have been reannealed to a Cot value of 20 moll× sec/1 to study the distribution of the intermediate DNA on the MAK column. Intermediate DNA contains two components, one (CsCl density after reannealing, 1.703 g/ml) obtained by reannealing high molecular weight DNA, the other (CsCl density after reannealing, 1.707 g/ml) obtained only by reannealing sonicated low molecular weight DNA. High molecular weight intermediate DNA (1.703 component) is eluted early from the MAK column in the fractions corresponding to the main DNA peak, while low molecular weight intermediate DNA (1.707 component) is more widespread on the MAK column, but appears to be enriched in the fractions eluted later. The possibility is discussed that the latter component is interspersed in that part of the genome which is apparently more homogeneous in density in an analytical CsCl gradient, and is absent on the skewed, more heterogeneous, heavy side of the main DNA in CsCl.