The prevalence of IgG antibodies to spotted-fever group rickettsiae was studied in a sample of 1055 healthy children aged 2-17 years, residents of the desert Negev region of southern Israel. Groups of children from 5 different places of residency were tested: (1) urban children from the city of Beer-Sheva; (2) children from Omer, a suburb of the city; (3) children from rural communes ("kibbutz"; (4) children from small agricultural settlements ("moshav"; and (5) seminomadic bedouin children. Overall 40 sera (3.8% were positive by the indirect immunofluorescent antibody assay at a titer of 40. The prevalence rate was 3.6% in males and 4.0% in females. Age-specific prevalence rates for the 2-5, 6-9, 10-13 and 14-17 year old groups were 2.0, 5.4, 4.1 and 3.6% respectively. The prevalence rates by place of residency were: urban 3.3% suburban 3.3% "kibbutz" 3.8% "moshav" 5.1% and seminomadic children 3.3% and did not differ by socio-economic status as measured by degree of crowding. The results indicate that spotted fever is endemic in all human habitats in the Negev region. Our data do not support association to sex or socio-economic status of the children tested. Lack of cumulative prevalence rates with increasing age suggests that antibodies may wane to undetectable levels in the years following the infection.