Summary. In order to harmonize laboratory results in the field of general medical biochemistry at the national level, analyti- cal methods and analytical quality goals based on biological criteria together with common reference intervals were recom- mended. The following parameters are included: general biochemical parameters (metabolites and substrates, enzymes, electrolytes, microelements, proteins, lipids), routine urine and stool analysis and laboratory haematology and coagulation. The main purpose of external quality control in medical biochemical laboratories is to ensure independent and objective evaluation of laboratory test results in order to promote harmonization and achieve a high degree of interlaboratory compara- bility. The recommended reference intervals were produced on a representative sample group of urban population in Croatia for school children, adolescents and adults. For pediatric population, reference intervals were recommended according to the literature data. The recommended laboratory methods and corresponding reference intervals in the field of general medical biochemistry have to be used in all medical biochemical laboratories in Croatia since January 1, 2005.