To estimate the incidence of Haemophilus influenzae type b (Hib) invasive disease in Italian infants we performed a prospective study in a cohort of newborns enrolled for a randomized trial on safety and efficacy of three pertussis vaccines and followed for onset of serious disease or pertussis. The overall cumulative incidence observed in 15,601 children was 51.3/100,000 for all invasive Hib infections and 38.4/100,000 for Hib meningitis, over 27 months of observation. The incidence density of all invasive Hib disease was 28.7/100,000 person-years, while meningitis occurred with an incidence of 21.5/100,000 person-years. Among the eight cases detected, six were meningitis, one sepsis, and one cellulitis. The child with sepsis died. The incidence and epidemiology of invasive Hib disease in Italy are comparable to those reported from other European countries. Cost-benefit analyses are needed for planning Italian vaccination policy.