The study was carried out to describe the epidemiology of the scarlet fever occurring in Lao Cai in 2009. The results show that: the cases distributed through all age groups but dominated by groups 10 - 15 (178/100.000), 5 - 9 (144,3/100.000), 1 (79.5/100.000) while prevalence of group 15 years old was the least. Regarding risk of infection, there was no difference between men and women. The cases distributed differently among districts and higher in rural than in urban area (76.9/100.000 vs 19.4/100.000). The outbreak occurred from February to May and got its peak at day 12 from its onset and included rubella, measles and rashes cases at the proportion of (41.6 percent, 7.8 percent, 50.6 percent respectively). There were cases who had received measles vaccination but still being suffered from scarlet fever (rubella, measles, rashes). Rate of having history of exposing to scarlet cases was high (76.8 percent).