OBJECTIVE To describe the etiologic study of the pertussis-like syndrome, not only as far as Bordetella genus is concerned but also regarding the causative role of other microorganisms for a 11-year period (1988-1998). METHODS In all specimens from patients suffering from pertussis-like cough the presence of Bordetella spp., other bacteria, viruses, and mycoplasma was investigated. The analysed data included microbiological findings and epidemiologic issues (age, sex, hospital admission area, yearly distribution and seasonal period). RESULTS A total of 1,063 specimens were investigated, most of them nasopharyngeal aspirates (910), corresponding to 905 patients; a positive culture was obtained form 56.9 of these patients. B. pertussis was isolated from 10.5% of patients. As for other bacteria, Haemophilus influenzae and Streptococcus pneumoniae were also isolated, in 16.9% and 15.8% of occasions, respectively. The respiratory syncitial virus was isolated from 10.7% of patients and other viruses in 9.4%. Among mycoplasma, Ureaplasma urealyticum predominated, with a recovery rate of 2.9%. The male/female ratio was 495/410; the ages of 67.2% of patients ranged from 0 to 6 months; a total of 689 (76.1%) required hospital admission. The recovery of B. pertussis and adenoviruses predominated during spring and summer months. In contrast, H. influenzae, S. pneumoniae and respiratory syncitial virus were recovered more frequently during winter months. CONCLUSIONS Most patients with pertussis-like syndrome are children aged less than 6 months. The recovery percentages of B. pertussis and respiratory syncitial virus are identical and therefore we think that the investigation of their presence in this syndrome is fully warranted as well as the search for other microorganisms, since clinical symptoms are commonly non-specific among infants.