Total nucleic acid (TNA) and deoxyribonucleic acid (DNA) of degenerating and stimulated sciatic nerves of rabbits have been determined. The ratio DNA/TNA in normal nerves was 0.59. In degenerating nerve the total nucleic acid content increased during the first 96 h, though there was little increase in DNA, the increase being presumably mainly in the fraction containing ribonucleic acid (RNA). On the contralateral side the TNA content remained unchanged, but the DNA/TNA ratio decreased to a small extent. After stimulation of the sciatic nerve for 4 h TNA remained unchanged but DNA decreased markedly.