Fixed metaphase chromosomes of the eel Anguilla anguilla were treated with the restriction enzymes Haelll, HinfI, and MseI. All three restriction endonucleases are capable of inducing a G-band-like pattern if the incubation time and enzyme concentration are controlled. The results are discussed in relation to the main factors involved in the appearance of serial G-bands. Chromatin organization, rather than DNA composition, seems to account for the interstitial G-band pattern exhibited by these eel chromosomes.