Objective: The assessment of using the Friedewald formula in LDL-cholesterol determination by participants of interlaboratory comparison program. Method: We shiped control samples to 187 participant laboratories together with questionnaire dealing with problems of the LDL-cholesterol determination by use of Friedewald equation. Three questions were listed in this questionnaire. Results: 43 % of participants used Friedewald formula for LDL-cholesterol calculation. Eleven different modifications of this equation were reported. Concentration of triglycerides limited using this equation ranged in interval 3.5–10.0 mmol/l. 30% of participants used too high triglycerides values as limitation for this equation (≥ 5.0 mmol/l). Also procedures used if equation cannot be applied, are too different, from using the direct LDL-cholesterol measurement up to not providing laboratory results (78%). Conclusion: In spite of fact that Friedewald equation is a standard methodological tool for the determination of LDL- -cholesterol in international medical guidelines, the state of using this equation in our laboratories is very poor. Commonly recommended and accepted formula does not exist. Reasons for this fact are totally unclear.

        Key words: LDL-cholesterol, Friedewald equation, interlaboratory comparisons, international guidelines.