Cryopreserved porcine hepatocytes in collagen cultures secreted albumin (up to 98 +/- 3 mug ml(-1); non-cryopreserved controls: 100 +/- 9 mug ml(-1)) and metabolised diazepam (67.5% +/- 7.5% of initially applied diazepam are metabolised; 77.5% +/- 10% in non-cryopreserved controls) for up to 14 days after thawing. The cultures resembled the recently developed flat membrane bioreactors. Addition of 5% (v/v) serum did not effect diazepam metabolism. Hepatocytes in collagen-sandwich cultures offer a storable liver support system for potential clinical use.