Toxicity of contaminated sediments collected from an old sawmill area and the downstream river-lake system was assessed with three different bioassays. Survival and growth were used as endpoints in subchronic (10-day) test with Chironomus riparius and growth and reproduction in long-term (28-day) test with Lumbriculus variegatus. A microbial bioluminescent direct contact assay, the Flash test, was also included in the test set to measure acute toxicity. In every bioassay, sediment from a pool of the sawmill was found to be toxic, and some adverse effects were found in other sediments as well. The bioassays were then compared to chemical analysis results, which showed the presence of several toxicants. These results could not, however, be directly connected to any individual toxicant, nor did they show any obvious trend downstream from the mill.