Rice is largely self-fertilized and accordingly a field population of rice is completely composed of near homozygotes.Due to the emergence of off-types,homozygosity will be affected.With the time,this will cause the reduction of genetic purity in some rice varieties.One of the reasons has been suspected to be the high out-crossing frequencies of such varieties.Studies were conducted at the Rice Research and Development Institute,Batalagoda,Sri Lanka to estimate the out-crossing rote of Bg 379-2,a variety having the problem of maintaining genetic purity.Bg 379-2 was allowed to out-cross with Bg 450 and the number of outcrossed plants were counted using dominant morphological markers such as short-round grain and purple culm of pollen donor.A molecular confirmation of out-crossing was also performed using sequence tagged site (STS) molecular marker pTA248.The variety Bg 379-2 showed a potential out-crossing rate of 3.41％ and an average out-crossing rate of 1.29％ using dominant morphological markers.Polymorphism was clearly detected between parents and out-crossed plants as well as selfed plants of Bg 379-2 using their banding patterns.A similar study can be performed to determine the out-crossing rates of other varieties which show high percentage of off-types in the population for the better understanding of the breeding behavior of the varieties.