Vitamin K3 (VK3) and vitamin C (VC) produce reactive oxygen species, mitochondrial depolarization and nuclear morphology indicative of apoptosis in lymphocyte and leukemia cells. Lymphocyte, Jurkat and K562 were incubated with increasing concentration of VK3 (A) and VC (B) for 24 h. Nuclear morphological changes was evaluated using AO/EB staining. Inset: Representative fluorescent photomicrography shows cell shrinkage and rounding, chromatin condensation (arrows), nuclei fragmentation (arrowheads) indicative of apoptosis and necrotic cells (asterisk) in K562 cells treated with (35 μM) VK3 (A) and (1 mM) VC (B). The ANOVA showed significantly differences among the three cells groups, p < 0.0001; post-hoc comparison showed significantly increase in cell death morphology in the leukemia cells on each VK3 and VC concentration versus lymphocytes. Jurkat cells were incubated with (10 μM) VK3 (C) and (10 mM) VC (D) for 24 h. Cells were evaluated for O2.-/H2O2 production, Δψm and nuclear morphological changes indicative of apoptosis. NBT+ stained blue-purple precipitate cells, DCF+ green fluorescent cells, DiOC6(3)high/low+ green fluorescent cells and apoptotic nuclei percentage is expressed as mean of percentage (%) ± S.D. from three independent experiments. ANOVA test for each condition showed differences among groups p < 0.0001. The post-hoc comparison showed increase in number of DCF, AO/EB and NBT+ cells, whereas the number of DiOC6(3)+ cells decreased in a concentration-dependent fashion. One-way ANOVA analysis with Bonferroni post-hoc analysis was performed. A p-value of ap < 0.05 and bp < 0.001 Jurkat versus K562 or cp < 0.05 and dp < 0.001 versus lymphocytes (A, B) or control (C, D) was considered significant.