ISO 9001 quality management systems is one of globally well-known standards developed by the International Organization for Standardization (ISO). It is widely implemented in different organisations, regardless of their size class and sector of activity. The aim of this study is to collect and analyse information on mechanical engineering enterprises by size classes in Latvia that have been certified in conformity with ISO 9001 requirements. This study presents findings from the research focused on mechanical engineering. Therefore, an overview of the most popular management system standard in the mechanical engineering sector has been done. A comparative analysis has been applied in order to determine the proportion of enterprises with quality management systems certified in accordance with the ISO 9001 standard by industrial sector in Latvia and worldwide. The expected research outcome is a distribution of mechanical engineering enterprises by size classes (micro-, small-, medium-sized and large-scale enterprises) in Latvia certified with ISO 9001.