The incidence and duration of hypertriglyceridemia (HTG) associated with allogeneic HLA-identical bone marrow transplantation (BMT) were investigated in 38 patients with normal triglyceride levels (TG) before BMT and without any evidence of prior liver disorder. Twenty-two (58%) patients developed HTG. The median of TG peak values was 350 mg/dl (range 215-908) and the median actuarial time for HTG appearance was 7 weeks (range 1-12). Among several variables analysed (age, sex, hyperglycemia, total parenteral nutrition, treatment with methylprednisolone, estrogens or cyclosporine A) only cyclosporine A administration was significantly associated with HTG development.