Levels of polychlorinated byphenils (PCBs) were monitored continuously in Zagreb between June 1999 and February 2000 and analysed qualitatively and quantitatively using high resolution gas chromatography (HRGC). Total PCBs were determined with respect to Aroclor 1260, which was used as the standard reference. The concentrations of PCBs ranged from 1.6 to 136 pg/m3 and were higher in warmer seasons (temperatures above 10 degrees C; 5.1-136 pg/m3) than in colder seasons (temperatures from -10 degrees C to about 10 degrees C; PCB range: 1.6-23.5 pg/m3). The increase in PCBs concentration with temperature followed an exponential curve.