Prerandomization renal biopsy specimens were examined in 102 patients upon entry into prospective therapeutic trials of lupus nephritis in an attempt to identify early predictors of renal failure outcome. All 11 renal failures occurred among the 72 individuals with diffuse proliferative or membranoproliferative glomerulonephritis (DPGN/MPGN); thus, these patients were at modestly, but significantly, increased risk of endstage renal disease compared to those with focal proliferative, membranous, or mesangial glomerulonephritis. Considering the low incidence of endstage renal disease among patients with DPGN/MPGN, we sought to refine the prognostic information obtained from renal morphology by semiquantitative scoring of individual histologic features and by derivation of composite histologic scores specified by Activity (AI) and Chronicity (CI) Indices. Among the 72 patients with DPGN/MPGN, the composite AI was more strongly predictive of renal failure than were the individual active histologic features; cellular crescents and extensive fibrinoid necrosis yielded positive associations, while endocapillary proliferation, leucocytic exudation, and hyaline thrombi in glomeruli and interstitial inflammation by themselves did not emerge as useful prognostic indicators. However, chronicity items (glomerular sclerosis, fibrous crescents, tubular atrophy, and interstitial fibrosis) considered individually, as well as in the composite CI, were highly predictive of renal failure outcome. Particularly striking was the prognostic value of tubular atrophy; all 11 renal failures were among the 43 patients with tubular atrophy on prerandomization renal biopsy. While no single pathologic variable improved outcome predictions among those with tubular atrophy, examination for interactions among variables revealed that glomerular sclerosis and cellular crescents had a synergistic effect which augmented the prognostic information derived from analysis of tubular atrophy alone.(ABSTRACT TRUNCATED AT 250 WORDS)