In approximately 10% of the children suffering from juvenile chronic arthritis (JCA), rheumatic iridocyclitis was also diagnosed. In 90 JCA and iridocyclitis patients we studied relative risk, clinical course and prognosis by means of several clinical and immunological parameters. Antinuclear antibodies (ANA), selective IgA-deficiency, oligoarthritis type of onset of the disease and manifestation of JCA during infancy--predominantly in girls--were quite often accompanied by a pronounced susceptibility to rheumatic iridocyclitis, while seropositivity (RF-positivity) and systemic onset of juvenile chronic arthritis normally rule out rheumatic iridocyclitis. Among HLA-B27-positive boys of school age, the acute course of rheumatic iridocyclitis, which rarely results in serious and lasting complications, is more frequent; in some cases juvenile sacroiliitis or ankylosing spondylitis are evident. The evaluation of the risk factors makes it possible to systematically define subgroups likely to develop chronic iridocyclitis and less susceptible groups of patients, thus facilitating early diagnosis and treatment as well as clinical observation of the development of chronic iridocyclitis.