The juice of Phyllanthus emblica and its dialyzate were examined for their inhibition on formation of N-nitrosomorpholine (NMOR) in vitro and N-nitrosoproline (NPRO) in vivo. Addition of 2 ml of the juice dialyzate (JD) to a system containing 22 mumols/L NaNO2 and 22 mumols/L morpholine was found to effectively block NMOR formation, with the inhibition of 93%, while only 49.2% of inhibition was observed from the low concentration of vitamin C (VC, 20.5 mumols/L), which is equal to those present in the JD. Moreover, the inhibition was not affected by precipitating JD with plumbous acetate and gelatin. In rats garaging with NaNO2 and proline (40 mumols/L), co-administration of 1.3 ml of the undialyzed juice containing 36 mumols/L of VC reduced the urinary excretion of NPRO from 69.62 nmol/L to 4.24 nmol/L. Similarly, it was found in human studies that 13 ml of the juice dramatically diminished the NPRO excretion from 75.10 nmol/L to 22.79 nmol/L in the 24-hr urine of 12 healthy volunteers, who had ingested 300 mg NaNO3 and 500 mg proline. Again, the juice showed a higher inhibition in both cases in inhibiting NPRO synthesis than the equivalent of VC solution. The results suggested that only a fraction of inhibition is accounted for by VC in the juice, whereas the rest might contribute to some unknown non-phenolic inhibitors, which are worthwhile further identifying.