Antimicrobials are a standout amongst the most usually prescribed medicines. However, they are often excessively and inappropriately used, which can lead to adverse effects (including fatality in a few cases) in individuals and the community as well. The duration of antimicrobial therapy needs to be sufficient to control the microbial infection and prevent relapse. The aim of this study is to estimate the duration of antimicrobial therapy in various infectious disease conditions and identify commonly prescribed antibiotics in infectious diseases. A Prospective Observational Study was conducted for one year (December 2013 - December 2014) on the patients diagnosed with infectious diseases of both sex and mean age of 39 ±16.8 years in a super specialty hospital, Hanamkonda, Warangal, Andhra Pradesh, India. During the study period a total number of 2500 patients were reviewed, among them 752 patients were enrolled in the study who has met the inclusion criteria. Among the patients enrolled, 456 (60%) patients were males and 297 (48%) patients were females. In total, of collected 7 infectious diseases, the longer duration of antibiotic treatment was required to diseases like pancreatitis and malaria that is around 18 days followed by liver abscess of 13 days, typhoid fever of 11 days and gastroenteritis and pneumonia with 10 days each. The shortest duration of 9 days of antibiotic therapy is sufficient for UTI.