Serum and synovial fluid (SF) levels of serum amyloid A (SAA) and C-reactive protein (CRP) were measured in 46 cases of various inflammatory arthritis (Group 1), and in 40 cases of noninflammatory arthritis: 18 cases of osteoarthritis (Group 2) and 22 cases of traumatic arthritis (Group 3). Serum and SF SAA levels were markedly elevated in Group 1: 126.4 micrograms/ml +/- 19.2 SEM and 46.4 micrograms/ml +/- 10.5 SEM, respectively; moderately elevated in Group 2: 10.1 micrograms/ml +/- 2.9 SEM, 4.0 micrograms/ml +/- 1.1 SEM and moderately elevated in Group 3: 10.4 micrograms/ml +/- 1.2 SEM, 4.0 micrograms/ml +/- 1.2 SEM, respectively. Serum/SF SAA ratios were similar in all 3 groups and ranged between 2.52-2.72. In comparison to SAA, the increment of serum and SF CRP above normal levels was moderate. A positive strong correlation was found between serum SAA and serum CRP: r = 0.64 (p less than 0.001) and between SF SAA and SF CRP: r = 0.59 (p less than 0.0001). SF SAA did not correlate with the number of SF white blood cells but did correlate with the percent of SF polymorphonuclear cells: r = 0.23 (p less than 0.05).