The positions of preferential DNA interaction with the nuclear matrix were mapped within the domain of the chicken alpha-globin genes in transcriptionally active erythroblast nuclei and inactive nuclei of mature erythrocytes. In the latter, only two major distinct attachment sites were observed, close to the A + T-rich sequences previously found at the boundaries of the domain. Sequencing of these structural matrix attachment points revealed several known DNA motifs; some of them were present on both sides of the domain. In actively transcribing erythroblast nuclei of adult animals, a large fraction of the transcribed area was represented in nuclear matrix DNA, including upstream and downstream elements. In particular, adult alpha A- and alpha D-globin genes were found in matrix DNA, while the transcribed but translationally unexpressed embryonic pi gene was underrepresented. The data are discussed in terms of the existence of stable or structural and expression-related matrix attachment sites; correlations to the origin of replication and the units of transcription of the domain are shown.