The resurgence of AFP in various experimental models was followed by serological, light and electron microscopic methods. The animal models included (a) liver regeneration after partial hepatectomy (70% resection) of mice and rats; (b) liver intoxication by carbon tetrachloride (CCl₄) of mice and rats; (c) liver intoxication by N-nitrosomorpholine (NNM) of rats; (d) chemical hepatocarcinogenesis by NNM of rats.