The diagnosis of sudden infant death syndrome (SIDS) is less than 100% certain in any given instance. Approximately 90% of all SIDS have occurred by age 6 months. A visual aid consisting of 1,000 dots helps in communicating numerical information such as 'rates' to parents (and others as well). The annual and seasonal occurrence patterns are independent of so-called SIDS risk factors. A single, major gene defect cannot account for SIDS but the root cause may be genetic (polygenic). Recent estimates of sibling risk to SIDS indicate that earlier estimates were inflated. Use of apnea monitors to prevent SIDS has no basis in fact but may provide emotional support. DTP immunization does not cause SIDS.