The aim of the study was to investigate different procedures to check for the most effective disinfection method and most dimensionally accurate impressions post-treatment with disinfectant. Five alginate impressions, each of thirty-two dentate patients were made with 24 hours interval. Impressions were divided into five categories: Group I included alginate impression with only water rinsing (Control). Group II were with immersion in chlorhexidine gluconate solution, Group III were spraying and Group IV were impression of alginate mixed with chlorhexidine solution. Group V comprised of impressions taken after pre-procedural mouth rinsing. Samples were inoculated in blood agar media for 3 days at 37°C. The impressions were poured in type III dental stone. The inter-molar distance, inter-canine distance, the antero-posterior distance and the depth of the cast were measured with Digital Vernier calipers. The results indicate the presence of highest number of bacterial colonies on Group I impression i.e. the control group. Least bacterial count was found in Group V followed by Group III, Group II and Group IV. Highest dimensional changes were seen in Group IV followed by Group III and Group II casts. Group V was found to be most dimensionally stable. Within the limitations of the study, it was concluded that the most effective and accurate method of disinfection is pre-procedural rinsing followed by spraying and immersion. Internal disinfection was found to be the least effective method with high bacterial count as well as high dimensional changes.