Acute rheumatic fever (ARF), is a systemic inflammatory disease etiologically related to infection with group A beta hemolytic streptococcus, characterized by a broad spectrum of disorders in cellular immunity. To estimate the activity of the immunopathological process in patients with ARF, plasma nitric oxide metabolities (NOx) concentrations, IL-1alpha and IL-2 levels were investigated in 22 patients with ARF at the time on admission, and after 3 months, in children with chronic rheumatic heart disease (CRHD). Plasma NOx concentrations, IL-1alpha and IL/2 levels in patients with ARF on admission were significantly higher than in the same patients 3 months later, and higher than in CRHD, or controls. Increased plasma NO may be a useful index for the quantitative assessment of the activity during immunological challange. This information may be useful for the prognosis and monitoring of ARK. (C) 2003 Tohoku University Medical Press.