Levels of persistent organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were determined in the blood serum of people living and working in the urban area of greater Rio de Janeiro city. Blood samples from 33 volunteers (16 males, 17 females, 19-63 years old) were taken in January 1999. OCP residues (op'DDT, pp'DDT, pp'DDD, pp'DDE, Aldrin, Dieldrin, Endrin, Heptachlor, Heptachlor-epoxide, alpha-, beta- and gamma-Hexachlorocyclo-hexane, Hexachlorobenzene) and PCBs (congeners: 28, 52, 101, 138, 153, 180) were extracted with n-hexane and analyzed by gas chromatography with electron capture detection. Except for pp'DDE (detection limit = 1.4 microg/L) no other OCP residue was found in the samples. No PCB congener (detection limit = 2.0 microg/L) was detected either. pp'DDE was found in 17 out of 33 samples in concentrations that ranged from 1.4 to 8.4 microg/L of serum or, on a fat basis, from 0.200 to 3.452 microg/g of serum lipids. Percentage of positive samples (%) and levels of pp'DDE (range of positive samples) increased from the youngest to the oldest group (< or = 29 yrs: 10%, 0.278 microg/g; 30-39 yrs: 60%, 0.200-0.765 microg/g; > or = 40 yrs: 77%, 0.257-3.452 microg/g).