The mitotic and lampbrush chromosomes of the domestic fowl and Japanese quail were analysed by fluorochrome staining technique. The lamphrush chromosomes of both the species displayed a typical "loop-chromomere" structure. Three distinct kinds of loops were distinguished in Gallus g. domesticus - normal, telomeric bows, and lumps. The former are distributed along the whole chromosome length. The latter and the bows were observed in subtelomeric and telomeric regions. By DNA/RNA specific acridine orange staining it was shown that each loop (especially, "lumpy" loops) contained a rich RNP matrix. A comparative analysis of the chromomycin A3/distamycin A banding pattern of mitotic and lampbrush chromosomes shows that the telomeric "bows" and "dumps" are special loops developed in telomeric heterochromatic bands. In Coturnix c. japonica, the CMA/DA-positive bands were not observed in telomeres of mitotic macrochromosomes, except a smallest band in the 2p-arm telomere. The absence of telomeric heterochromatic bands which can be visualized in the quail mitotic chromosomes coincides with the absence of "bow"-like loops. Only small lump-like structures were seen in some telomeres of macroautosomes. The biological significance of loop formation and RNA synthesis in heterochromatic band loops in growing oocytes is briefly discussed.