Objectives : The serum total cholesterol is supposed to be increased as dietary pattern is westernized recently in our country. We studied the longitudinal change of serum total cholesterol levels in normal adult Korean male workers and analyzed the influence of lifestyle on change of serum total cholesterol levels. Methods : The 7677 healthy adult male workers were studied during recent 5years(1992 and 1997). Those who suffered from hypertension, diabetes mellitus, ischemic heart disease, nephritis were excluded. Those who ingested antilipidemic drugs were also excluded. Serum total cholesterol were measured by the same enzymatic method and their levels were analyzed during fasting state. Data on lifestyle were obtained using self administered questionnaires. Results : 1) The serum total cholesterol levels increased by 9.45±23.99mg/dl(1.89mg/dl per year) between 1992 and 1997 surveys. 2) The increment of serum total cholesterol levels was most prominent in the twenties (3.45mg/dl per year) and less prominent in 5th, 6th decades. 3) A change of 1kg/m2 in body mass index contributed a change of 3.449mg/dl in serum total cholesterol. 4) The change of body mass index(BMI) was most significantly correlated with that of serum total cholesterol levels among the influencing variables.( =3.449 p=0.0001 r2=0.035) 5) The changed value of serum total cholesterol levels was significantly correlated with smoking and exercise, however, was not significantly correlated with the amount of alcohol ingestion. Conclusion : The serum total cholesterol levels increased by 9.45mg/dl(1.89mg/dl per year) during recent 5 years. The increment of serum total cholesterol levels was more prominent in younger age group. The changed value of BMI was most strongly correlated with that of serum total cholesterol levels of all influencing variables.