Thirty-six of the 39 children originally described with the syndrome of seronegative enthesopathy and arthropathy, followed for a mean of 11 years after symptom onset, were found to have had a widely varied clinical course. Twelve of the 23 patients (52%) who originally did not have a seronegative spondyloarthropathy developed definite (6) or possible (6) seronegative spondyloarthropathies. The development of a seronegative spondyloarthropathy was associated with HLA-B27 (p = 0.0004) and the presence of arthritis (rather than arthralgia only) at the time of the original report (p = 0.05). For patients with arthritis, the development of a seronegative spondyloarthropathy was associated with arthritis onset after 5 years of age (p = 0.01).