PURPOSE: The value of eosinopenia as a test in favour of an infectious disease was suggested by Schilling since 1929. We tried to verify this hypothesis with a prospective and multicentric study. PATIENTS AND METHODS: One thousand and thirty-eight patients were included (82 females and 56 males, means age: 71.8 years). Diagnoses were: 83 infectious diseases, 38 systemic diseases, 10 neoplasia and 7 miscellaneous. RESULTS: The mean value of eosinophils was 72/mm3 in bacterial infectious diseases and 214/mm3 in non infectious diseases (p < 0.01). When leukocytes were higher than 10,000/mm3 and eosinophils counts less than 40/mm3, predictive value for an infectious bacterial disease was 100% as well as specificity. Under same conditions, when protein C reactive was higher than 100mg x l(-1), the predictive value was 85% and the specificity was 57%. CONCLUSION: Our study shows that an inflammatory syndrome associated with hyperleucocytosis above 10,000/mm3 and eosinophils counts under 40/mm3 seems strongly related to bacterial infectious diseases.