Most bioartificial liver devices utilise primary hepatocytes alone although some have considered the use of non parenchymal cells in addition. However the effects of co-culture of human hepatocytes with different sinusoidal cell types has not been fully investigated. In this study we have examined the influence of co-culturing primary human hepatocytes with the human hepatic stellate cell (HSC) line, LI90. Cultures were monitored by light microscopy and on days 4, 8 and 14 urea synthesis and cytochrome P450 activity were measured. Morphologically LI90 cells proliferated to fill spaces between and into adjacent islands of hepatocytes. On day 14 cytochrome P450 activity in co-culture was significantly improved compared to hepatocytes cultured alone. By contrast, urea synthesis in hepatocytes was unaffected by single or co-culture. Therefore it can be concluded that a combination of primary human hepatocytes with LI90 cells is beneficial for growth and some stability of hepatocytes and may therefore be appropriate for seeding bioartificial liver devices.