The NAD-glycohydrolase activity of freshly isolated adult rat liver cells nuclei was studied as affected by the ionic (dodecyl sulphate and deoxicholate) and non-ionic (Triton X-100 and digitonin) detergents as well as by ultrasound (15 and 22 kHz). The obtained data permit the detergents to be divided according to the character of their effects on the nuclear NADase activity into "decreasing" and "increasing" ones. Dodecyl sulphate and to a less extent deoxicholate are in the first group of the detergents. Triton X-100 and much more digitonin are in the second one. Sonification of the rat liver cells nuclei (15 and 22 kHz) from 3-10 s and further induced a decrease in the NADase activity with its subsequent complete loss. The treatment of the intact nuclei suspension with DNase leads to a 50% decrease in the NADase activity and the treatment of the sonificated nuclei suspension-- to a complete loss of the activity. Undet these conditions RNase does not affect the NADase activity.