Purpose: To study some growth indices and dental caries status of twins of kindergarten, Ulaanbaatar city.Methods: The study group consists of 7 pairs or 14 twins and control group consist of 14 children, who were same aged and same classmates of twins. The body weight and height of all children was measured by anthropometric methods and dental examination was done by WHO criteria 2003. The plaque index was determined by Pederov-Volodkini and caries activity was determined by Shimono (1974).Results: 1. The average body weight of study group was lower than control group, but the average body height of study group was higher than control group (p<0.01). 2. The mean deft score 6 dft, 7 dfs in study group and 8 dft, 12 dfs in control group, respectively (p<0.05). 3. Satisfactory of oral hygiene index was 64% in study group and 57% in control group (p<0.05). 4. When we determined the caries activity, high caries activity group was 50% in study group and 57% in control group (p<0.01). Conclusion: The risk factors and scores of dental caries of twin were lower than the control group. In the future we have to carry detailed study to relationship between body weight and mean dft score.