Purpose. Free radicals are implicated in the pathophysiology of aging, ischemic injury and neurodegenerative disorders. To deform]no whether Hominis Placenta extract prevents $H_2O_2$-induced apoptosis, we have performed morphological and biochemical analyses for the detection of apoptotic phenomena in the pineal tumor cell line $PGT-{eta}$ We have also peformed cytochemical and immunocytochemical analyses for the detection of changes in nitric oxide synthase (NOS) activity and estimated the expression . of apoptotic genes using reverse transcription-polymerase chain reaction (RT-PCR) Methods. $PGT-{eta};cells$ were pretreated with Hominis Placenta extracts $(0,;10^{-2};{mu}g/ml)$ for 2 hours and then exposed to $H_2O_2;(0,;50;{mu}M)$ for 3 hours. Appearance of apoptotic characteristics were monitored using 4, 6-diamidino-2-phenylindole dihydrochloride (DAPI) staining assay, terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling (TUNEL) assay and flow cytometric analysis. NOS activity was measured by NADPH-diaphorase cytochemistry. Expression of inducible NOS (iNOS) and nuclear factor kappa B (NF k B) was assessed via immunocytochemistry. The expression of apoptotic genes was examined by RT-PCR. Results. After 3 flours of exposure to $H_2O_2$, it was shown that $PGT-{eta};cells$ treated with $H_2O_2(50;{mu}M)$ exhibit classical apoptotic features and increases in NOS activity and caspase-3 expression. Treatment with Hominis Placenta extract resulted in a reduced occurrence of apoptotic features. DAPI staining, TUNEL and flow cytometric assays revealed decreases in the occurrence of nuclear fragmentation and in the sub-Gl fraction in the $PGT-{eta};cells$ treated with Hominis Placenta extract. Cells treated with Hominis Placenta extract also showed lower activity of NADPH-diaphorase and immunoreactivities of both iNOS and NF k B than those of $H_2O_2$-treated cells which were not treated with Hominis Placenta extract. By RT-PCR, it was shown that the level of caspase-3 mRNA was derreased In the cells treated with Hominis Placenta . extract. Conclusions. This study shows that Hominis Placenta extract prevents $H_2O_2$-induced apoptosis in $PGT-{eta};cells$; inhibitions of iNOS and caspnse-3 are possible mechanisms of the protection against apoptosis.