Evaluation of the obesity- and smoking-related atherogenic risk in an obese population, was studied by retrospectively reporting the 6-month dietary effect on metabolic lipoprotein parameters. In a non-smoker group, a weight reduction programme exhibits a marked improvement (P less than 0.05) of HDL and LDL cholesterol and atherogenic index. Smoking during successful, therapeutic weight reduction inhibits this advantageous improvement of lipid parameters, especially in women. In regard to the lipoprotein related vascular risk, obesity treatment without modifying smoking habits is less advantageous.