The clinical courses of 33 pregnancies in 24 patients with biopsy proven membranous glomerulonephritis have been analyzed. Twenty-four percent (8) of pregnancies resulted in fetal loss, 43% (14) in premature delivery and 33% (11) in a live birth after 36 weeks gestation. Maternal renal function declined during pregnancy in 9% (3) of the pregnancies and in 46% (15) hypertension developed. In 55% (18) proteinuria increased significantly during pregnancy. In 30% (10) nephrotic range proteinuria was recorded in the first trimester. Presence of nephrotic range proteinuria during the first trimester correlated with both poor fetal and poor maternal outcome (p less than 0.0004 and p less than 0.0002, respectively). It is concluded that pregnancy in patients with membranous glomerulonephritis is associated with increased fetal loss and, in some instances, a worsening in maternal renal function. The literature on this topic is reviewed in relation to these findings.