The expression of m-fas/apo1 (CD95) and its soluble form (s-fas) was studied in patients with early onset pauciarticular (n = 23) and systemic juvenile chronic arthritis (n = 7). RNA was prepared from peripheral blood of patients and 22 healthy controls and from 23 samples derived from the synovial fluid of JCA patients. The ratio of m-fas/s-fas transcripts was calculated by densitometry of fas-specific RT-PCR products. An inverted ratio of m-fas/s-fas transcripts was found in PBMC and mononuclear cells from the joints of early onset pauciarticular JCA patients. The m-fas/s-fas ratios were similar in PBMC and mononuclear cells from synovial fluid. PBMC from patients with a systemic JCA showed the same m-fas/s-fas ratio as healthy controls, with an inverted ratio of both transcripts in cells from the synovial fluid. The data indicate a role of Fas/Apo1 regulated apoptosis in EOPA-JCA which is not limited to the affected joints.