Primary rat hepatocytes were cultured in a flat, hollow-fibre cassette, 'The Tecnomouse', which provided direct oxygenation and a homogeneous environment for cells within the cassette. Most hollow fibre systems utilise media oxygenators to provide O-2 to cells; in the Tecnomouse cassette, cells are provided with direct oxygenation via gas channels in the silicone membrane surrounding the hollow fibres. Hepatocyte functionality was monitored by following urea production, albumin production and cytochrome P-450 enzyme activities. The system could maintain cells in a viable state and the presence of specific hepatocyte functions including albumin production and cytochrome P-450 activity. Electron microscopy showed aggregated spherical hepatocytes and apparent high extent of necrosis.