Hypocholesterolaemia is a frequent and typical phenomenon of many acute situations such as injury, severe infection associated with sepsis and septic shock, catabolic situations after serious operations , in myocardial infarction and neoplastic diseases. This phenomenon cannot be explai- ned only by malnutrition or energy deficiency although they may participate in the development of hypocholesterolaemia. In the development of thementioned acute conditions participates ac- cording to our opinion also impaired synthesis of cholesterol as well as of intermediary metabo- lites of its biosynthesis ( isoprene, squalene, lanosterol, and lathosterol). Evidence was provided that deprivation of these metabolites is frequent, very marked and statistically significant. Some precursors of cholesterol biosynthesis are extremely important for normal processes in the cell and as mediators (isoprene, farnesyl diphosphate, squalene ).Their deficiency is a serious disor- der which must be diagnosed in time. It is important to define the patients and conditions where a serious deficiency of these metabolites develops regularly and to seek ways how to treat depri- vation of the mentioned metabolites.

        Key words: Cholesterol - Isoprene -Cholesterol biosynthesis -Parenteral nutrition - Critical states.