Of 65 unselected SLE patients from a defined population, 61 were sequentially followed for two years with an SLE supervision programme. The cumulative clinical manifestations included a relatively high frequency of pulmonary vascular disease and gastrointestinal involvement. Flares were more common during the summer season and a change in the clinical manifestations occurred in 10 of 16 patients with major flares and in 4 of 13 patients with minor flares. ESR, S-orosomucoid, S-CRP, and C1r-C1s-C1 IA complexes, indicating C1 activation, were shown to distinguish inactive from active disease. The prevailing overall benignancy was reflected in a low mortality rate, limited need for treatment or hospitalisation, and good response to moderate dosages of corticosteroids in severe flares. The proportion of patients in gainful employment was comparable to that in the normal population, though absence due to sickness was more common in the SLE group. Joint complaints and mild psychiatric disturbance were the most common causes of enduring incapacity.