Two cases of Burkitt cell leukaemia (ALL3) occurring 60 and 51 months respectively after treatment of Hodgkin's disease (HD) are described. Clinical, cytological, immunological and cytogenetic features in these patients were comparable with those of the 6 previously published cases and with de novo ALL3. The prognosis of these secondary ALL3 is uniformly poor: our 2 patients died 2 and 14 days after the start of combination chemotherapy, and all the other cases survived less than 60 days after diagnosis. The significance of ALL3 occurring after HD is discussed: the association is probably not fortuitous, and its pathogenic mechanisms probably differ from those intervening in secondary myeloid leukaemias.