This case-controlled study examines some recently implicated risk factors for Sudden Infant Death Syndrome (S.I.D.S.) in Irish infants. Irish S.I.D.S. infants are lighter at birth than controls (3463g) compared to (3542g) and boys out-number girls by a ratio of 1.3:1. S.I.D.S. infants are more frequently: breast-fed (42% vs 25%) and sleep in a location other than the parent's bedroom (54% vs 21%), but start solids at a similar age and appear not to be sicker prior to death than the control group. This study highlights the frequency of symptoms of possible ill-health (i.e. snuffles and being "chesty") in well infants during the first months of life with 32% of the control group having snuffles and 35% described as "chesty". In addition these symptoms are frequently treated with antibiotics with 31% of the control group having already received antibiotics by 2 months of age. A majority of S.I.D.S. infants were described as cold when found (52%) with 39% described as warm and 15% as sweaty. Obviously the recently implicated role of overheating may be relevant in the latter 15% of S.I.D.S. cases. In this series, 88% of infants had died by 6 months of age. Of the 97 parents of S.I.D.S. infants questioned, 78 had subsequently become pregnant by the time the study was conducted at an average time of 5 months post the S.I.D.S. event.