In a previous report, we investigated the several candidate substances which accelerate liver regeneration by using 70% partial hepatectomized rats. In this study, we focused on S-allyl-L-cysteine ​​(SAC), a type of sulfur-containing amino acid. It has been reported that SAC has antioxidant and anti-inflammatory activities. However, little is known about the SAC-induced cell proliferation in various cell types. The aim of this study was to evaluate the effects of SAC and some analogues on the restoration of liver mass in 70% partial hepatectomized rats. After 70% partial hepatectomy, rats treated with SAC (300 mg/kg/day, p.o.) showed a 1.2-fold increase in liver weight per 100 g body weight on day 3 compared with saline-treated control. In contrast, S-methylcysteine (300 mg/kg/day, p.o.) or cysteine (300 mg/kg/day, p.o.) did not have a regeneration-promoting effect. In comparison with control rats, the regenerating liver of SAC-treated rats showed a significantly higher 5-bromo-2’-deoxyuridine labeling index on day 1. These results demonstrate that SAC significantly promotes the regeneration of liver mass via stimulation of hepatocyte DNA synthesis, but not that of antioxidant activity in 70% partial hepatectomized rats.