Abstract Gac (Momordica cochinchinensis (Lour.) Spreng) (2n = 28) belongs to the Cucurbitaceae family. It is indigenous throughout in Vietnam as well as in South East Asia. To estimate the genetic diversity, 20 gac accessions collected in Mekong river delta were analyzed using 10 RAPD primers. Total of 126 fragments were obtained from ten RAPD primers, with 114 polymorphic fragments, and average of 11.4 fragments per primer. The high level of polymorphism (90.4%) was found across 20 gac accessions. The high est Nei's gene diversity value among gac accessions was H = 0.40, and the lowest was H = 0.29 with a mean of 0.36. The highest Shannon diversity index value among gac accessions was H' = 0.58 and the lowest was H' = 0.46 with an average of 0.53. Cluster analysis for genetic relationship between accessions displayed that 20 gac accessions grouped into four main clusters which genetic distance coefficient ranged from 0.29 to 0.64 and with an average of 0.54. There were defined groups according to their locations. According to these results, RAPD technique can be useful tool in genetic diversity evaluation of gac. The information achieved could also be useful for gac breeding program, cultivar differentiation and conservation
