Thirty-nine patients with systemic lupus erythematosus (SLE) and diffuse proliferative glomerulonephritis have been enrolled in a multi-centre randomised controlled prospective study of chronic 4L plasma exchange therapy performed every three to four weeks. In the patients randomised to the pheresis (P) group and who received either albumin or plasma as replacement, there was a difference of 33 per cent better renal function at this time in the study. This difference did not achieve a significance with a p value of less than 0.05. However, the 30 patients randomised into the P group to receive albumin replacement did demonstrate a 50 per cent difference from the C group which was significant at a p value of less than 0.045. This also correlated with a statistically significant reduction in immune complex titres in the P versus the C groups. Chronic 4L plasma exchange with albumin replacement may be a useful therapeutic adjunct in patients with SLE and diffuse proliferative glomerulonephritis.