Background and objectives: Leptospirosis is a very common zoonosis in the world. Early diagnosis of leptospirosis is critical because just early treatment will be effective. It's culture is very slow and serological assays are not applicable because of lack of antibodies in the first week of the disease, therefore PCR is the only option for the early diagnosis. In this study, sensitivity and accuracy of a non-quantitative conventional PCR for diagnosis of leptospirose in first week sera of patients, is evaluated

  Methods : Seventy first week sera sample of patients with clinical diagnosis of leptospirosis which were negative in MAT but positive for the second time after one weeks (seroconversion) were selected and studied.

  Results : We observed twenty four positive sera in PCR test. Sensitivity of the test was 74.5% and accuracy was 100 bacteria /ml.

  Conclusion : Result of our study shows that PCR is the only choice for the early diagnosis of Leptospirosis while other assays are not applicable but its sensitivity is low.