It is well known that the results from clinical laboratories support diagnosis, prognosis and patient treatment. Thus, test results must be relevant, accurate and reliable for patient care. Despite all the automation, errors that are classified as pre-analytical, analytical and post-analytical, are still present. International bibliographic data estimates that approximately 62.0% of the errors made in clinical laboratories are due to errors during the pre-analytical stage. The effect of the pre-analytical errors on the laboratory results has consequences that in many cases can lead to reduction of laboratory quality. In this study, the authors run a failure modes and effects analysis (FMEA) to analyze potential failure risks within the pre-analytical phase, in order to classify them according to severity and likelihood, based on the experience. In the present article, the authors performed an FMEA analysis of the pre-analytical phase of the testing process of a biochemistry laboratory.