Secondary school students ages is one of the most physically strong of the development stages. Besides, the girl students have menstruation. However, the axis hypothalamus pituitary - ovarian action has been not stable in the few years, so that they have. menstrual disorders. They maybe have anemia if their menstrual disorder occurs in long time of
without providing adequate nutrition in time. Therefore, the assessment of red blood cell is necessary, so that the authors study this research in order to: Survey some index of red blood cell among female students in secondary school in Thai Nguyen province. Object and Method of study: Cross-sectional descriptive study. Object study include 2 groups (n= 607): group 1 are female students in urban school in Thai Nguyen city. Group 2 are female students of the secondary rural schools in Thai Nguyen. Result: - Index HGB, RBC, HCT, MCV in urban and rural schools are in normal limits. Index MCH, MCHC lower than normal limits. Students have not anemia, but red blood cells have hypochromia. - The difference between the two areas: In the urban, index HGB, HCT increases with age. In urban school, index HGB, HCT increases with ages. In rural schools, HGB of students which have menstrual is lower than students without menstrual. Index HGB, MCH, MCHC of students of the secondary schools in urban are higher than students of rural schools. The results show that, nutrition for students in urban is better than students in rural. The results show that, It has the different nutritional status between rural and urban. Nutritional quality have not really ensure for development of children, so red blood cells of students of the secondary schools district in Thai Nguyen had hypochromia. Therefore, the study should be more caring to the girls at this age, especially girls student of the rural.