The aim of this paper is to estimate the infant mortality rate and the incidence of sudden infant death syndrome (SIDS) in Lombardy, Northern Italy, in the period 1990-2000 and to provide basic information for a subsequent comparison of the SIDS incidence before and after the risk-intervention campaign. A retrospective epidemiological study was carried out using all deaths of resident infants occurring up to 1 year of age as recorded by the health districts mortality registries of the Lombardy region, between 1990 and 2000. The infant mortality rate was 4.1 per 1000 live births, with a significant decreasing trend. This decrease is mainly due to the fall in mortality for congenital malformations and perinatal diseases. The SIDS incidence rate was 0.13 per 1000 live births; the annual incidence of SIDS during the study period decreased significantly by 60% from 0.20 to 0.08 deaths per 1000 live births (P = 0.001). When 'possible SIDS deaths', not directly labelled as SIDS, were also considered, the rate of SIDS was 0.54 per 1000 live births. The incidence of SIDS in Northern Italy appears much lower than anticipated. SIDS remains the single leading cause of death in the first year of life after the early neonatal period.