Lecithin:cholesterol acyltransferase (LCAT) is instrumental in high-density lipoprotein (HDL) maturation, but high LCAT levels do not predict low cardiovascular risk. LCAT may affect antioxidative or anti-inflammatory properties of HDL. We determined the relationship of plasma high-sensitivity C-reactive protein (CRP) with LCAT activity and evaluated whether LCAT activity modifies the decreasing effect of HDL cholesterol (HDL-C) on CRP, as an estimate of its anti-inflammatory properties. Plasma HDL-C, apolipoprotein (apo) A-I and LCAT activity (exogenous substrate method) were measured in 260 nondiabetic men without cardiovascular disease. CRP was correlated inversely with HDL-C and apo A-I, and positively with LCAT activity (P<0.01 to 0.001). Multivariate regression analysis demonstrated that age- and smoking-adjusted plasma CRP levels were associated negatively with HDL-C (beta=-0.224, P<0.001) and positively with LCAT activity (beta=0.119, P=0.034), as well as with the interaction between HDL-C and LCAT activity (beta=0.123, P=0.026). There was also an interaction between apo A-I and LCAT activity on CRP (beta=0.159, P=0.005). These relationships remained similar after adjustment for apo B-containing lipoproteins. In conclusion, the inverse relationship of HDL-C with CRP is attenuated by LCAT activity at higher HDL-C levels. It is hypothesized that LCAT could mitigate HDL's anti-inflammatory or antioxidative properties at higher HDL-C concentrations.