Purpose: Immigrant junior-field-workers in south eastern Anatolia, Turkey, had an impact on agriculture economy, and to provide an optimal dental service is crucial due to their multiple medical and dental problems. So, a combined preventive-operative method including ART-fissure sealant/restoration and fluoride varnish application was evaluated in terms of caries increment, cariogenic bacteria and lesion behavior at one-year follow-up period. Materials and Methods: A total of 27 children with 147 pit and fissure lesions displaying discoloration were included in this study. Of these, 15 children with 75 lesion and 12 children with 72 lesions were divided as test and control groups, respectively. Baseline caries values of each groups were 3.4 ± 1.4 and 2.5 ± 1.6 for test and control groups respectively (p 0.05). Bacteriologic sampling was undertaken with the dip-slide method (Vivadent). A combined preventive-operative method was performed for the test group but not for the control group. After six months and one year, children were re-examined with respect to cariogenic bacteria in plaque, new caries occurrence and lesion characteristics. Results: Mean caries increment (ΔDMFT) for both the control and the test group were 1.91 ± 1.53 and 0.26 ± 0.43, respectively. The difference was found to be statistically significant (t = 8.35, p 0.0001). More lesions in the control group did progress to cavitation than in the test group. A linear relationship was observed between plaque MS-score and cavitation, indicating that when plaque MS levels are high, cavitation does easily occur in the control group and vice versa in the test group (p 0.0001 for all variables). Conclusion: It could be argued from these findings that a combined preventive-operative method could be applicable not only to treatment of dentinal lesions but also to retard, even prevent, the initial caries on pits and fissures of permanent teeth in rural districts where any other routine dental/preventive care is not feasible, and compliance of the individuals' hygiene is inadequate. Keywords: ART (Atraumatic Restorative Treatment), fluoride varnish, pit and fissure caries, lesion behavior