The Promotion Thesis studies the aspects affecting conformity assessment and the changes made over time to ensure that only compliant and safe products are used. The aim of the Promotion Thesis is to identify management problems and offer new solutions thus improving the conformity assessment system, in order to raise awareness about conformity assessment, to make conformity assessment processes clearer for entrepreneurs and to ensure placement of safe products on the market. In the first part – the theoretical aspects of quality and conformity assessment are studied. In order to improve the terminology used in the conformity assessment field, different definitions of related terms are generalized and analysed, basing on which proposals are made for translations of the terms, new definitions are given and the current definitions are made more precise. The totality of aspects characterizing product quality is evaluated, information gathered on interrelationships of quality management and product conformity assessment process. In the second part – evaluation of technical harmonization approaches and their comparison is made, conformity assessment system in Latvia and the European Union is evaluated, conformity assessment of measuring instruments is evaluated from the theoretical and practical point of view, the main problems of conformity assessment system management and problems related to product conformity assessment are identified. In the third part – solutions for elimination of the identified problems and improvement of conformity assessment system management are elaborated. The necessity to make use of uniform methodology is substantiated, and the Technical Harmonization Approach that would substitute the current approaches of technical harmonization is developed. Conformity assessment system scheme is improved and a method developed to be used by manufacturers when selecting the most suitable of conformity assessment modules. Proposals are made that would foster the responsibility of the involved parties and the society thus excluding use of non-conforming products. The Promotion Thesis comprises 176 pages, including 36 figures, 5 tables. The Promotion Thesis has 12 appendices. 204 sources, which are included in the Sources of Reference, have been used when developing the Promotion Thesis. The thesis has been developed with the support of the European Social Fund for the project "Support for the Riga Technical University for doctoral studies".