Late blight caused by Phytophthora infestans seriously damages tomato grown in cool and high humidity seasons. Based on artificial inoculations with various locally isolates collected in major areas cultivating tomato of Vietnam, gene Ph3 shows a good resistance to the pathogen. Otherwise, gene Ph1 and Ph2 are overcomed by local isolates. The results from phenotyping of parents, Fl, F2, and backcross populations indicated that gene Ph3 was partially dominant. By four backcrosses, gene Ph3 from tomato accession L3708 has been succesfully transfered into the recurrent parents. Besides, the breeding programs with an assistance of the molercular marker have developed several tomato lines. They are homozygous gene Ph3, highly resistant to late blight and carrying good fruits (oval or round shapes, medium size), high potential yield (50-60 tons/ha).