Background: This study aimed to examine the reliability of larvae free index taken from periodical monitoring as compared to that of dengue hemorrhagic investigation (DHF) epidemiologic investigation at primary health centers.Methods: This was an analytic cross sectional study with a sample of all dengue fever officers stationed at ten primary health centers in Denpasar. Mean in percent difference was used to measure reliability between the two indices. Spearman correlation coefficient was used to measure the correlation between age and assignment duration with larvae free index.Results: The results found a larvae free index of 95.7%, which exceeded the expected national target of 95%. Epidemiologic investigation implemented by officers assigned at every village resulted in a larvae free index of 95.6 %. Mean difference between both larvae free indices was 0.2%. Officerâs age and assignment duration had weak correlation with larvae free index, with correlation coefficient of 0.3 and 0.1, respectively.Conclusion: Larvae free index taken from periodical monitoring in Denpasar 2007 showed a high reliability with that taken from epidemiologic investigation. Larvae free index in Denpasar in 2007 was above 95%, an indication that should reduce the spread of DHF in the endemic area. Jurnal Kedokteran Indonesia: 1 (1): 83-87Keywords : Reliability, Larvae free Index, Larvae Periodically Monitoring, Epidemiologic Investigation