The work presented in this article focuses on the environmental impact of hydraulic fluids used in forestry. Migration and biodegradability of three biolubricants and a mineral lubricant were monitored in two forest soils and in a liquid medium. These studies proved that biolubricants were easily degradable products and showed ultimate biodegradability rates significantly higher than those of the fluid of mineral origin, specially in a soil environment. This superiority was even greater when fluid behaviour was observed after 1000 h of use. Ecotoxicity test enabled the classification and comparison of biolubricants and showed that toxicity levels of the biolubricants were never high however, even after use, as compared to petroleum-based fluid. (c) 2008 Elsevier Ltd. All rights reserved.