The Carotid Atherosclerosis Italian Ultrasound study (CAIUS), a multicenter, double-blind clinical trial, performed in 305 asymptomatic, moderately hypercholesterolemic patients, clearly demonstrated beneficial effects of pravastatin on the carotid intima-media thickness (IMT) progression. The database of the CAIUS study was examined in order to investigate the presence of a relationship, if any, between the activity of pravastatin on IMT progression rate and its hypocholesterolemic effect. Quantitative B-mode ultrasound imaging was used to quantify the individual mean maximum IMT progression rate in 3 years. In the overall group of patients (placebo and pravastatin) covariance analysis showed that while the variable 'treatment' (0 = placebo, 1 = pravastatin) was significantly related to the reduction of IMT progression (F= 6.6, P = 0.01), the IMT progression did not correlate with the extent of LDL-C lowering (F= 0.00, P = 0.98). To further investigate this issue. the pravastatin treated group was stratified into quartiles of LDL-C reduction. In contrast to what was observed in the placebo group, in which a positive mean IMT progression rate was observed, independent of the extent of LDL-C reduction, no IMT progressionwas observed in any subgroup treated with pravastatin. No significant difference was found among quartiles and no trend could be identified. In conclusion, the effect of pravastatin treatment on carotid IMT progression rate is beneficial; however the CAIUS study demonstrated that lowering LDL-C by itself, does not explain the variability of beneficial changes in IMT.