Partial hepatectomy (PH) is known to enhance liver carcinogenesis when it is performed several hours before or after administration of a hepatocarcinogen. This effect has been attributed to cell proliferation, which is induced by PH and is a necessary step for fixation of DNA damage leading to initiated cancer cells. We now report for the first time that PH can also increase the tumour incidence, and decrease the latency period, when it is performed 8-10 weeks before treating rats with the hepatocarcinogen N-nitrosodiethylamine. This animal model may offer a tool for investigating the underlying mechanism of the 'memory effect' and increased tumour susceptibility of liver cells after PH. Additionally, it could be explored as a more sensitive rodent bioassay for testing putative carcinogens.