The early phase of rheumatoid arthritis has attracted increasing attention due to the concern with prognosis of the disease. In this study IgM rheumatoid factor (RF) and IgA immunoglobulin were measured twice a year in 96 patients. Their joint damage was assessed yearly with radiographic examination. Radiological abnormalities detected included osteoporosis, bone erosion and joint space narrowing. The patients were followed up for three years. The changes of joint damage might be of three types: worsening, nonchange and improvement. A significant correlation between the levels of IgM RF and IgA immunoglobulin and disease activity was observed. A high level of IgM RF was prognostic for a more severe disease. One patient with 7 g/L IgA immunoglobulin exhibited considerable joint damage progression in a year, while 2 cases with minor IgA immunoglobulin showed remarkable improvement. These two parameters can be considered the important laboratory indicators for the early disease. The results may also be applied to guide second line antirheumatic drug therapy.