We examined nonviral, lipid-mediated gene transfer methods as potential tools for efficient transfection of articular chondrocytes. Transfection conditions were determined for primary cultures of normal human articular, osteoarthritic human articular and normal bovine articular chondrocytes using a lacZ reporter gene construct with the commercially available cationic liposomes Cellfectin, DMRIE-C, LipofectAmine, Lipofectin, LipoTaxi, TransFast and the lipid-based reagent FuGENE 6. Optimized conditions were then evaluated in an ex vivo model of chondrocyte transplantation. FuGENE 6 transfection produced the maximum levels of transgene expression. Transfection efficiency was cell type specific and affected by DNA concentration, lipid/DNA ratio and the presence of hyaluronidase, a matrix-degrading enzyme. Analysis of X-gal staining demonstrated an efficiency of 41.0% in normal bovine articular chondrocytes, 20.7% in normal human articular chondrocytes and 7.8% in osteoarthritic human chondrocytes. Transfected chondrocytes were found to successfully populate the articular cartilage surface in explant cultures. Transplanted genetically modified chondrocytes adhered to the articular cartilage and continued to produce beta-galactosidase for 2 weeks. This evaluation and optimization of lipid-based gene transfer into articular chondrocytes may serve as a useful tool in studies of genes involved in articular cartilage damage and repair and as a potential delivery method for therapeutic genes. Gene Therapy (2000) 7, 286-291.