Abstract: Trans-stilbene, a chemical reagent, was found to be effective in protecting the liver from CCl₄ injury. In the first series of experiments, mice were given orally two doses of stilbene (100 mg/kg for each dose) in the first day and a dose of GCl₄ (0.01 ml/kg) the next day. The SGPT and SGOT levels as well as BSP retention were significantly lower in stilbene pre-treated mice than in the CCl₄ controls determined 16 hrs after injection of the liver poison. Histological examination revealed that lesions of the liver of stilbene pre-treated mice were less severe than those of CCl₄ controls. In the second series of experiments, a dose of CCl₄ was given to the mice and 40 hrs later the mice were given orally stilbene at dosages of 50 or 100 mg/kg twice a day for two days. The repair of injured liver tissue seemed to be accelerated since the liver weights and SGPT levels were statistically lower in the stilbene treated mice. These findings are parallel to the pathological observations.Since this compound did not show any effect in lowering either the SGPT levels or the GPT levels of liver tissue in normal mice at the dosage as high as 1000 mg/kg, the possibility of inhibition of the enzymes may be excluded.In the third series of experiments, mice fasted for 24 hrs were used. An hour after a dose of stilbene (100 or 200 mg/kg), mice were injected with 10% glucose (20ml/kg) and sacrificed 2 hours thereafter for the determination of liver glycogen. The results showed that glycogenesis was stimulated by the oral administration of stilbene. In adrenalectomized mice this action was even more significant: the liver glycogen in the stilbene (200 mg/kg) pre-treated mice was found to be twice as high as controls—a potency approximating 100 mg/kg of cortisone.No significant effect was found either on the pentobarbital sleeping time in mice (stilbene 200 mg/kg, p o) or on cotton pellet granuloma response in rats (stilbene 100 mg/kg/day p o for 7 days). However, the compound exhibited a very weak estrogenic activity as shown in the immature mice uterus assay.The toxicity of stilbene is low. When suspended in starch, the ip LD₅₀ was found to be 6.50±0.76 g/kg in mice. No death was recorded in 10 mice given an oral dose of 8.0 g/kg. When dissolved in oil the toxicity of stilbene increased sharply, the po LD₅₀ of its peanut oil solution was found tO he 0.92±0.14 g/kg. Four dogs (two males and two females) were fed stilbene 10～50 mg/kg for 30 days. No change in behavior, liver and kidney functions and blood counts was found.