An enzyme immunoassay (EIA) test system has been developed for the detection of tick spotty fever (TSF) group Rickettsia. A long scheme of immunization in an isogenic system on rabbits has been used with an adjuvant without bacterial components, and based on aluminum hydroxide. This EIA test system detects whole soluble R. akari, R. sibirica, and R. conorii antigens and is at least 10-20 times more sensitive than the indirect hemagglutination test. Treatment in a temperature gradient permits the detection of the corpuscular antigen. A considerable vector infection rate has been revealed in individual examinations of ticks in foci of tick rickettsiasis, whereas such studies carried out in nonendemic areas brought negative results.