Summary: DNA fragments of SO and 10 kbp were found in ischemic brain in adult rats following two-vessel occlu sion or in neonates following hypoxia-ischemia. These higher-order fragments were detected before any laddered oligonucleosomal DNA fragmentation characteristic of apoptosis. Both the SO-and 10-kbp fragments were also detected during necrosis produced by decapitation, but these led to smeared smaller fragments, not laddered pat terns. End-group analysis showed the presence of both 3' OH and S;-OH ends in both the SO-and lO-kbp fragments