Since the incidence of shaken baby syndrome in Switzerland was not known, we conducted a nationwide prospective follow-up study for a 5-year period (from 2002 to 2007). The data were collected through the Swiss Pediatric Surveillance Unit. Inclusion criteria were the presence, in a child <or=6 years of age, of 1) more than or equal to two clinical symptoms (altered consciousness, convulsions, respiratory irregularities, and bulging fontanel), 2) one eye finding (retinal hemorrhages, vitreous hemorrhages), 3) one MRI/CT finding (subdural hematoma, subarachnoid hematoma, and parenchymatous lesions), or 4) history of shaking. Exclusion criteria were age >6 years or documented accident/disease explaining symptoms/findings. To describe outcome, we used the King's Outcome Scale for Childhood Head Injury (KOSCHI). 56 cases were reported from 13 of 26 Swiss cantons, representing 80% of the Swiss population; 49 cases met the inclusion criteria. Preponderance of male infants was high (31 male and 18 female); median age at admission was 4 months (1-58). Clinical symptoms were present in 42 infants, retinal/vitreous hemorrhages in 39 infants, and pathological brain/head imaging in 46 infants. In 13 cases, the caregivers admitted shaking the child. Outcomes (KOSCHI 1-5; n = 47 patients) were death (KOSCHI 1) 8 (17.7%), vegetative state (KOSCHI 2) 0, severe disability (KOSCHI 3) 11 (22.2%), moderate disability (KOSCHI 4) 14 (31.1%), and good recovery (KOSCHI 5) 14 (28.8%). Based on these data, the incidence of shaken baby syndrome in Switzerland is 14 per 100 000 live births, which corresponds to the incidence in other Western countries. Demographic characteristics and outcomes of Swiss patients were comparable to published studies.