Purpose: Dental caries is the primary pathological cause of early tooth loss in children, which may lead to malnutrition and other health problems. Identification of patients with active carious lesions and at high risk for caries can help to dramatically decrease the disease prevalence. Thus, recognising the importance of early diagnosis of caries, the present study was carried out to correlate caries with oral microflora using Oratest among 12- to 15-year-old schoolchildren. Materials and Methods: A total of 100 children were divided into control and test groups (n = 50) according to their DMFT scores. The test group was further divided into subgroup 1 (DMFT = 1-3) and subgroup 2 (DMFT > 3). Oratest, a caries activity test, was performed on all the children. Comparison among the variables was done using ANOVA and the independent sample t-test. Results: Boys had lower DMFT values (1.35 ± 0.2) than did girls (1.67 ± 0.2) (p = 0.38), and the Oratest time was higher among boys (132.8 ± 0.5 min) than girls (126.4 ± 0.5 min) (p = 0.53). The control group had the highest mean Oratest time (172.7 ± 0.3 min), followed by subgroup 1 (97.8 ± 0.2 min), and subgroup 2 had the lowest Oratest time (68.5 ± 14.8 min). A statistically significant negative correlation (r = -0.893) was found between the mean DMFT and the Oratest time (p 0.001), ie, they were inversely related to each other. Conclusion: An inverse relationship exists between Oratest and DMFT score. Palabras clave: caries activity test, children, dental caries, Oratest