A prospective study of 9,864 male adults in Dakar, who were bled at four-monthly intervals, defined how clinical symptoms and α-Foetoprotein positivity in the serum relate in time. Nine cases of hepatoma were identified, of which seven could be examined repeatedly till death; one remained negative, three became positive the appearance of symptoms and three were positive before theappearance of clinical signs. Patho-biological aspects and practical implications as to earlydetection are discussed.