The aim of this study was to evaluate the influence of lipoprotein(a) levels and apoprotein(a) isoform size in determining the low cardiovascular risk of a rural, inland Sicilian population. Plasma levels of total cholesterol, LDL-cholesterol, HDL-cholesterol, triglycerides, lipoprotein(a) and apoprotein B and AI were measured in a sample of 278 subjects (141 males, 137 females) representative of a population of 1351 subjects (622 males, 729 females). The apoprotein(a) isoforms were also identified. Results indicated that the levels of the common lipo-apoliproprotein parameters were lower than those of other populations, while lipoprotein(a) plasmatic levels and apoprotein(a) isoform distribution were similar to those of other Caucasian populations. The distribution of lipoprotein(a) levels was skewed to the right, with a higher prevalence of low levels, the apoprotein(a) isoforms most strongly represented in our sample were of intermediate size (25-27 kringles IV). Univariate analysis showed that lipoprotein(a) levels were correlated to apoprotein(a) isoform size (R = -0.48, p < 0.001) and to the age of the subjects (R = +0.13, p < 0.01). In a multiple regression analysis, lipoprotein(a) levels were correlated to the apoprotein(a) isoform size of the homozygous isoforms or smaller heterozygous isoforms, while larger heterozygous forms were not correlated. In conclusion, our study showed that in our population, lipoprotein(a) levels and apoprotein(a) isoforms are similar to those of other Caucasian populations. Other factors, such as the physical activity of a rural population or the Mediterranean diet, must be considered in order to explain the lower cardiovascular risk of this population.