Several investigations have reported a prone sleeping position to be a risk factor for sudden infant death syndrome (SIDS). We investigated whether changes in sleeping position among infants in Northern Norway were associated with changes in SIDS rates. The prevalence of prone sleeping position was 54% among infants born in the years 1976-1989 and 5% among infants surveyed in May 1994. During the same period the SIDS rate declined from 2.75/1000 to 1.57/1000. These findings are consistent with other research in the field, and indicate that a prone sleeping position is a risk factor for SIDS.