The authors describe three cases of malignant degeneration observed within amygdaloid cysts in two male and one female patient aged sixty. In one of the cases in which the cyst had been present for more than two years, there was apparently some primary degeneration, the theory favoured was that of Veau's malignant branchioma; two other cases showed metastasis of a homolateral tonsillar epithelioma within an hitherto sub-clinical amygdaloid cyst.