OBJECTIVE Persistent organochlorine pollutants (POPs) from the environment are still bioaccumulating in human tissues. The aim of our study was to analyze the development of plasma POPs levels in obese women in relationship with their weight loss success in five year follow-up study. METHODS 20 obese women aged 25-73 years were studied just before and after having completed a 3 month controlled low calorie diet (LCD) intervention (5 MJ daily), and again after 6 and 60 months since the beginning of the study. Body weight and plasma levels of 7 POPs were measured: polychlorinated biphenyls (PCB) 153, 138, 180; 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethylene (p,p'-DDE); 2,2-bis(4-chlorophenyl)-1,1,1-trichloroethane (p,p'-DDT), hexachlorocyclobenzene (HCB), hexachlorocyclohexane β (HCH β). RESULTS Data shows that after 3 months of a completely controlled restrictive diet regimen, the weight loss was associated with an increase in POP plasma levels. However, after a five year follow-up, there were no differences in POPs plasma levels between those who kept losing weight or maintained the initial weight (WL/M) and the group of weight gainers (WG), except for HCB where the WG had a significantly higher level (p < 0.05). CONCLUSIONS These results suggest that contrary to the long-term weight gain, the long-term weight loss or weight maintenance caused by diet restriction is associated with lower plasma levels of HCB.