A prospective clinical study of 23 patients with giant-cell arteritis (GCA) and/or polymyalgia rheumatica (PMR) was undertaken in order to assess the behaviour of the non-specific markers of the disease activity, the erythrocyte sedimentation rate (ESR) and other acute phase markers, particularly the C-reactive protein (CPR) and serum amyloid A apolipoprotein (apo SAA) levels during induction of disease remission by prednisone therapy, and possible further recurrence of GCA and/or PMR. The apo SAA measurement is more sensitive than the CRP measurement in determining disease activity (97% and 61%, respectively). The specificity of apo SAA is greater than ESR in the determination of inactive disease (86% and 77%, respectively). In some cases with clinically active disease the ESR and CRP were normal, whereas the apo SAA was always elevated. We conclude that the apo SAA measurement in combination with clinical data and other laboratory parameters may be useful in the management of GCA and/or PMR.