The treatment records of patients on gold therapy have been studied with particular respect to the development of proteinuria. This was classified as mild (up to 0.3 g/1), moderate (0.4–2 g/1), or heavy (more than 2.0 g/1). Particular attention was paid to the mode of onset and prognosis of the proteinuria and to subsequent gold administration. Twenty-seven patients with moderate or heavy proteinuria were identified. Two were suffering from psoriatic arthropathy, the rest were diagnosed as having rheumatoid arthritis, although three were persistently sero-negative. There was a direct correlation between the degree of proteinuria and its duration. Heavy proteinuria persisted for at least three months, whereas moderate proteinuria cleared within this period. No patient developed permanent renal impairment. Nine of 10 patients with heavy proteinuria had preceding mild or moderate proteinuria during which period gold administration had been continued. Fourteen of 17 patients with moderate proteinuria had their gold injections continued or re-started and none of these subsequently developed heavy proteinuria. It is suggested that moderate proteinuria should lead to cessation of gold therapy until the urine is clear but that subsequently treatment may be safely re-started.