In 1993, a large-scale investigation of polychlorinated biphenyls (PCBs) in Baltic Sea sediments was performed in cooperation between the Baltic states. sPCB (IUPAC # 52, 101, 118, 105, 153, 138, 180) in surficial sediments increased from north (mean 213 ng g⁻¹ C) to south (mean 382 ng g⁻¹ C), indicating atmospheric influence. In contrast to decreasing PCB trends in pelagic biota, the sPCB in dated sediment cores from the Baltic proper showed increased or constant concentrations during recent decades. Down-core congener patterns showed no changes during the 20th century. After re-calculation of sPCB deposition, assuming interannually variable dry matter deposition, the sPCB sediment deposition trend matches the observed sPCB concentration trend in Baltic biota although the reductions in recent decades are less for the sediments. A calculation of sediment burial of sPCB indicated that laminated Baltic proper sediments are efficient traps, and a mass balance showed that the sPCB retention time in the water mass is less than one year.