The purpose of this study was to examine longitudinally the different patterns of nuclear and cytoplasmic antigen recognition by sera from patients with SLE during clinical flare and remission using immunoblot-ting (1B) techniques.Serum samoles (n =150) were obtained from 35 SLE Datients during a follow-uu period averaging 4.7 years. Three patients (10 sera) were in complete remissibn: the IB paitern of these 3 patients remained unchanged; 32 SLE patients experienced one or more clinical flares: in 5 cases (20 sera) the 1B analysis showed no detectable antibody. The following dominant IB patterns were seen in the remaining 27 active SLE patients: anti-Sm (n= 7), anti-Sm/RNP (n= 7), anti-SS-B and/or anti-Ro (n= 6), anti-histones (n= 5), anti-70 Kd (unidentified) (n= 2). No IB pattern was able to differenciate mild forms of SLE from severe cases. In 9 of 21 clinical flares, the serum IB pattern was not different from that of the patient's serum drawn during remission (3 severe and 6 mild flares). Diversity of the antibodies increased in 7 cases (5 severe, 2 mild flares); and a shift from one pattern to another was observed 5 times (2 severe, 3 mild flares). Twenty three subsequent remissions were studied: in 14 cases the IB profile was unmodified (5 severe, 9 mild SLE), and the diversity of the antibody narrowed in 4 cases (2 severe, 2 mild SLE). The IB pattern shifted from one pattern to another (2 severe, 4 mild SLE) in 5 instances. These data suggest that the antinuclear antibody IB pattern of each SLE patient remains roughly unmodified during clinical flares and remissions but differs widely from one patient to another.