Twenty-two patients with constellation of features suggestive of systemic lupus erythematosus (SLE), but who did not qualify by "criteria" or a rheumatologist's intuition as having SLE, have been followed prospectively for at least 5 years, and have been labeled latent lupus. These patients presented with at least one of the 1971 or 1982 classification criteria, plus any of a constellation of minor criteria. They differed from patients with SLE in the absence of renal and central nervous system disease, and the lower frequency of DNA antibodies and depressed complement. They had a similar distribution of HLA antigens. Seven of the 22 patients evolved into SLE during the period of followup. There were no clinical or laboratory features which distinguished these patients from the remaining 15 with persistent latent lupus. Patients with latent lupus may represent a mild spectrum of SLE, and evolutionary phase of classic SLE, or a diathesis awaiting other provoking factors.