Extensive forest fires occurred in Catalonia, northern Spain, in 1994. In our study, concentrations and profiles of 12 parent polycyclic aromatic hydrocarbons (PAHs) were determined in riverine waters, ash and sediment samples at nine sampling sites (W1-W9) and at three sampling dates from Llobregat hydrographic basin: in August, 1994, one month after the extensive forest fires; in September, 1994, after the first heavy autumn rainfalls and in January, 1995, six months after forest fires. In August 1994, the total concentrations of 12 PAHs measured in riverine waters varied from 2 ng/l to 336 ng/l. In September 1994, the total PAH concentrations decreased to 0.2-31 ng/l and in January 1995, from 9 ng/l to 73 ng/l. In August, the composition pattern of PAHs showed a distribution dominated by 4-ring PAHs (pyrene, chrysene+triphenylene, benzo(a)anthracene) at W3-W6, W8 and W9 and 3-ring PAHs (phenanthrene) at W1, W2 and W7. In September, a preference by 3-ring PAHs (phenanthrene) at all sampling sites except W5 was shown and in January was clearly dominated by 4-ring PAHs (chrysene+triphenylene, pyrene, benzo(a)anthracene) at all sampling sites. In ash and sediment samples, the total concentrations of 12 PAHs ranged from 1.3 ng/g to 19 ng/g. The dominant compound was phenanthrene.