Background: Microscopy is an important tool for diagnosing malaria and is considered to be the gold standard for malaria diagnosis. However, a number of studies have shown that routine microscopy in Africa is often inaccurate. WHO (2010) has recently recommended that wherever possible malaria treatment should be dependent on a parasitological confirmation of malaria. This constitutes a major shift in policy away from presumptive treatment for malaria of all fever. In this context the accuracy of parasitological testing is becoming a key issue for successful implementation of the new policy. Objective: To evaluate the accuracy of malaria microscopy in district hospitals in Tabora region, Tanzania and to identify reasons for any failure to reach WHO minimum standards of accuracy. Material and Methods: An analytical cross sectional study was conducted among five district hospitals in Tabora, including malaria microscopists, Convenience sampling was used. Targets of 100 slides were selected for repeat expert examination and 27 laboratory staff were interviewed. Data analysis: STATA-10 was used for analysis. Results: 27 laboratory staff were interviewed, 51% were men, it was observed that the quality of malaria routine slides was poor due to poor staining, precipitates and slide scratching. The laboratory environment were often inadequate due to excessive noise and inadequate space. The results of ten reference slides suggested that while most readers were correct in <90% of slides, 25% of staff were correct in <60% of slides. Laboratory assistant scored 50% better than laboratory technicians and attendants. None of the hospital laboratories was a functioning quality assurance programme for blood slide microscopy. Results dissemination: The results will be used to inform policy makers of the needs to improve routine blood slide results before new policies are introduced to restrict malaria treatment to those with a positive blood slide or rapid test for malaria. Conclusion: The quality of routine malaria slides was poor and the general performance of test mostly were good, the laboratory environment was inadequate and microscope condition was good then diagnosis needs to be improved, and quality assurance must be effectively practiced in order to improving laboratory performance.