This investigation was begun 1 mo after a spill of 2000 tons of Iranian crude oil polluted shores along the west coast of Norway in February 1976. It is based on mass-fragmentographic analysis of naphthalene, methyl-, dimethyl-, and trimethylnaphthalenes, phenanthrene, methyl- and dimethylphenanthrenes, dibenzothiophene, methyl-, dimethyl-, and trimethyldibenzothiophenes. Samples of stranded oil, water, and seven species of benthic organisms were collected periodically during the following year. During the 1st mo of weathering the total amount of these aromatic compounds had decreased from 1.22% in the original oil to 0.76%, with a further decrease to 0.2–0.3% during the next 3–4 mo. In the water the concentration of these compounds was approximately 2 μg/L (ppb) at the start of the sampling. At one of the investigated locations a chemical dispersant was used in cleaning the shores. This resulted in higher concentrations of the aromatic compounds in the water, up to 12 μg/L. The organisms studied had accumulated aromatic hydrocarbons up to an excess of 20 μg/g wet weight, 1 mo after the spill. Although seasonal and individual differences were large, the dibenzothiophenes appeared to be retained to a larger extent relative to the naphthalenes and phenanthrenes. Key words: oil spill, benthic organisms, naphthalenes, phenanthrenes, dibenzothiophenes, mass fragmentography, petroleum