We report the case of a 41-year-old man diagnosed with Still's disease. Multiple disease-modifying anti-rheumatic drug (DMARD) therapies failed to induce disease remission or to prevent progressive joint destruction. The man presented with active arthritis and classical Still's rash accompanied by fever. Anti-tumour necrosis factor-alpha (TNFalpha) therapy was planned but during the medical check-up prior to the biological therapy, renal insufficiency with marked proteinuria (PU) was discovered. With PU of 912 mg/24 h a renal biopsy was performed and a histopathological evaluation revealed the diagnosis of a residual mesangio-proliferative immunocomplex-based glomerulonephritis (GN). After excluding contraindications, infliximab therapy was initiated and a good response of the arthritis was documented after 6 weeks. A significant decrease in PU (279 mg/24 h) was noted after the third infliximab infusion. Because of an allergic reaction during the fifth dose, the infliximab was discontinued. During the time frame without anti-TNFalpha therapy, active joint disease reoccurred and the proteinuria increased significantly. Because of the active disease entanercept therapy was initiated. The arthritis diminished and the PU was reduced markedly within 4 weeks. In the follow-up period of 12 months a good response to therapy was sustained. As described by other investigators, the joint disease showed a rapid and sustained response to anti-TNFalpha therapy. The decrease in proteinuria during biological therapy was notable. It was concluded that the significant decrease in PU in this patient was achieved by eliminating the inflammatory activity of the underlying kidney disease.