Salmonella spp. isolates from faeces and organs of postweanlng pigs with diarrhea in 9 industrial farms, in 6 Northern provinces of Vietnam comprised 5 serotypes. S. typhlmurlum serotype made up 51.61 percent of the isolates, followed by S. anatum (19.35 percent), S. agona (16.14 percent), S. meleagridis and S. ruzizl (6.45 percent for each serotype). All of the isolates were resistant to streptomycin and most of them were resistant to tetracyciin, amoxicillln, ampicillin and sulfatrimethoprlme along with very high virulence. The snt gene coding for enterotoxin production and invA gene coding for invasion factor were detected in most of the isolates. These two genes were detected in all of the S. typhimurium isolates. The results indicated that S. typhimurium may play an important role in diarrhea symptom of pigs in the Northern provinces of Vietnam.