Serum amyloid protein A (SAA) levels were evaluated by a sensitive radioimmunoassay technique in leprosy, juvenile rheumatoid arthritis and chronic osteomyelitis. SAA was elevated in all 3 groups of patients. The level in each of the patient groups did not reflect the presence of secondary amyloidosis. Our study suggests that serum SAA protein levels should not be considered a routine diagnostic test in patients with chronic inflammatory diseases prone to the development of amyloid disease.