On 3/29/2001, the Baltic Carrier oil tanker collided with another vessel in the Baltic Sea southeast of the Danish island of Falster. The collision resulted in the spill of some 2400 ton of heavy bunker oil. A monitoring program was carried out to assess the levels of oil and ∼ 80 different polycyclic aromatic compounds (PAC) in water, sediment, and biota samples and to form the basis for ecotoxicological assessments. In April 2001, PAC levels in seawater from the Grønsund were of the range 641-12,833 ng/L with a median value of 1115 ng/L. Even after 2.5 mo, PAC concentrations in seawater had decreased to 2839-124 ng/L, which was close to baseline levels. The PAC level in blue mussels, Mutilus edulis, only decreased slowly. In June, concentrations of 132-1031 μg/kg (w/w) were measured, while levels in December were 185-498 μg/kg wet weight. The overall decrease in PAC body burden from June to December was due to excretion of light (2-3 ringed) and substituted compounds. Mussels sampled in December, on the other hand, had higher levels of many HMW parent compounds (4-6 ringed). PAC levels in shrimp from Grønsund decreased by a factor of 10 during the first year after the Baltic Carrier accident; this decrease was mainly due to a reduction in light (2-3 ringed) and substituted compounds. This is an abstract of a paper presented at the 26th Arctic and Marine Oilspill Program Technical Seminar (Victoria, British Columbia, 6/10-13/2003).