The dynamics of association-dissociation of the c-myc protooncogene-containing chromatin with the nuclear matrix (NM) were studied in rat liver cells during transient activation of the gene. The gene was activated by injection of cycloheximide (CHI) to animals. Two periods of the c-myc gene activation were found by RNA--DNA hybridization blotting during the first 12 h after the injection of CHI with the maxima at 3-4 and 9-10 h. The NM-associated chromatin was also found by DNA--DNA hybridization blotting to have two periods of an increase in the amount of the c-myc gene. The c-myc gene activation-inactivation dynamics during the first period were conjugated with the dynamics of its association-dissociation with the NM. During the second period the c-myc gene amount in the NM-associated chromatin was the same as during the first period but the transcriptional activity of the c-myc gene during the second period was significantly lower. The results suggest two activation stages of the gene(s): 1) the production of a topologically independent chromatin loop by the association to the NM; 2) the initiation of the gene transcription in the produced loop. Both stages seem to take place during the first period of the c-myc gene activation while during the second period only the first stage occurred and the second stage was only partially realized.