Four patients are described with hypocomplementemic persistent glomerulonephritis in whom serum β1c levels, initially low, rose and remained in the normal range for periods of months to years and then fell to their previous low levels. In two patients, the rise to normal was apparently spontaneous, and in two others it occurred during a course of immunosuppressive therapy. During the time the levels were normal, there were no signs that the nephritis was healing or static. In fact, in one of the patients, renal function deteriorated during the time when the level was normal, and in another, deterioration occurred shortly after the level fell. The observations indicate, first, that the serum β1C level is not infallible as a diagnostic hallmark of the entity known as hypocomplementemic persistent nephritis and secondly, that there is no clear correlation between the serum β1C level and the rate of the progression of the nephritis.