Hyaluronan (HA) is a fundamental component of many biomaterials. Reports on the biological effects of HA are, however, both inconsistent and contradictory. This particularly refers to fibroblast contraction in the presence of high concentrations of HA. hi this study we used a broad range of molecular weight (MW) and concentrations of HA to assay its influence on human dermal fibroblasts in both two and three-dimensional culture models. High-MW HA in high concentrations demonstrated inhibitory effects on both cell attachment and proliferation. HA-coated surfaces appeared less adhesive to fibroblasts than collagen-coated surfaces. In the fibroblast-populated collagen lattice, HA supplementation dose-dependently retarded gel contraction, which was associated with reduced cell division and spreading. Although gene transcripts of collagen type I and III were not significantly upregulated in the monolayer culture as determined by real-time PCR analysis, more type III collagen was present in HA-incorporated collagen gels by Sirius red staining. Type III collagen was homogeneously distributed and well organized in the presence of HA. Our data indicates that HA has both a qualitative and quantitative effect on cell-matrix interactions. Optimum parameters in terms of MW and concentration need to be determined when HA-based biomaterials are being prepared for tissue-repair purposes. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 90A: 11771185, 2009