Comparison between results of measurements of heterochromatic regions detected by differential C and DA/DAP1 staining and the hybridization data of two cloned repeated human DNA sequences one alphoid (pH S05) and the other the satellite DNA III (pPD18) on chromosome preparations was made. A positive correlation of heterochromatic region sizes on several chromosomes and the amount of label over them detected after hybridization with both alphoid and satellite sequences was shown, the correlation with the latter being more pronounced.