A visual analogue scale (VAS) and a 4-point scale (FPS) have been compared in patients suffering from prolonged constant pain due to chronic inflammatory or degenerative arthropathy. Each patient was treated with a constant low or high dose of paracetamol or dihydrocodeine throughout a four week period. The VAS was accurate, as reliable and more sensitive than the FPS in registering the intensity of chronic pain. Separate records of each estimate, sealed immediately on completion by the patient, resulted in omission of significantly more pain recordings on the FPS, whereas retention by the patients of their previous records did not systematically influence subsequent judgments. In this study, the VAS appeared to be more satisfactory than the FPS for patient self-rating of pain intensity.