Genetic variation of sal ( S. robusta ) was investigated in 3 natural populations in the Terai region, Nepal, using 12 loci from 8 isoenzyme systems. The mean number of alleles per locus was 2.16, and 58.3% of loci were polymorphic (95% criterion for polymorphism). The mean observed and expected heterozygosities ranged from 0.105 to 0.129, with an average of 0.117, and from 0.130 to 0.158 with an average of 0.143, respectively. Only 4.7% of the total genetic diversity was due to differentiation among the populations and the mean value of genetic distance was 0.018. The results suggested that the majority of species' genetic variation was found within the studied populations and there was high genetic similarity among the 3 natural populations of S. robusta . The sharing of one gene pool among the studied populations suggests a lack of barriers to gene flow.