We examined the ethnic heritage of 467 patients with amyloidosis and related it to the type of amyloid (secondary versus other types) found among 52,370 autopsies at Los Angeles County-University of Southern California Medical Center. Classification of amyloidosis by type was accomplished by using the potassium permanganate Congo red staining method and a specific anti-AA antiserum, supplemented by the anatomical distribution of the amyloid in some instances. We discovered a statistically significant increase in amyloidosis among patients with hispanic surnames as compared with other Caucasians. The overall rate for Hispanics in our total autopsy population was 2.3% as compared with 0.6% for other Caucasians (P less than or equal to 0.001). The increase was mostly among those whose amyloid was negative to tests for secondary (AA) amyloidosis and not anatomically compatible with senile cardiac (senile systemic) amyloidosis. Hispanics accounted for 76% of these cases as compared with 18.5% for Caucasians (P less than or equal to 0.001). Our findings, along with previously published reports, suggest that the frequency of amyloidosis may vary significantly in different ethnic groups.