We measured the serum levels of manganese-superoxide dismutase (Mn-SOD
) in acute myeloid leukemia (AML) and acute lymphoid leukemia (ALL). S
erum Mn-SOD level for normal subjects was 94.1 +/- 23.5 ng/ml (mean +/
- S.D.), the levels for AML and ALL patients were 159.6 +/- 77.1 ng/ml
and 154.4 +/- 77.0 ng/ml, respectively. The serum Mn-SOD levels were
unrelated to individual intracellular Mn-SOD levels, but correlated we
ll with serum lactate dehydrogenase values. Regression of the leukemia
was accompanied by decrease in the serum level of Mn-SOD. Serum Mn-SO
D may thus serve as a measure of the activity of the disease.