A comparative study of the total cholesterol (TC) and its fractions was carried out in 3 groups of males. The first group consisted of (C) 53 healthy males (18 between 30-39 years old, 17 between 40-49 and 18 between 50-65); the second group (M) was of 57 male doctors (19 between 30-39 years old, 21 between 40-49, and 17 between 50-65); third group (E) was of 94 males with myocardial infarction (22 between 30-39 years old, 32 between 40-49, and 40 between 50-65). TC was significantly lower (p less than 0.02 and p less than 0.001) in both the lower ages ranges in Group E compared to Groups C and M in all age ranges. Group M showed significantly lower (p less than 0.001) in Group E compared to Groups C and M in all age ranges. Group M showed significantly lower HDL-C (p less than 0.01) and to group M in the lowest age range (p less than 0.005). LDL-C was significantly higher (p less than 0.001) in Group M compared to C in the higher age range. VLDL-C was higher (p less than 0.05) in Group E compared to C in both the higher age ranges (p less than 0.05) as well as to the middle age range of Group M (p less than 0.05). The indexes TC/HDL-C and LDL-C/HDL-C were significantly higher in Group E compared to Groups C and M in all age ranges. These indexes were significantly higher (p less than 0.01 and p less than 0.05) in Group M compared to group C in all age ranges.(ABSTRACT TRUNCATED AT 250 WORDS)