To assess the effectiveness of child-resistant closures (CRCs) and unit dose packaging in preventing childhood poisoning with medications, a survey by 14 hospitals of accidental suspected poisoning in children under 5-years-old, was compared with a survey of a representative sample of households with children under 5 living in the catchment areas of the hospitals. Nine hundred and thirty-eight medications thought to have been ingested by 877 children were compared with 5827 medications found in households with children. The relationship between availability of packs or medications in the home and their involvement in accidents was quantified by means of an Accident Association Index (AAI). A low AAI indicated that the involvement of a pack or medication was less than expected from availability and therefore safe. A high AAI indicated that involvement was greater than expected and therefore unsafe. Medications involved in suspected poisoning were most frequently packed in containers without CRCs (63%) or transparent blisters (20%); both had high AAIs. CRCs, strips, sachets and opaque blisters had low AAIs. Analgesics, expectorants and gastrointestinal medications, had low AAIs, while oral contraceptives, hypnotics, sedative/tranquillizers, antidepressants, anticonvulsants, anti-emetics, and anti-infectives had high AAIs. Prescription medications were more frequently involved in accidents than over-the-counter (OTC) medications and had a higher AAI. Comparison of the AAIs of different kinds of medication in each of their various pack types showed that safe packaging reduced the risk from medications which had a high average AAI. Only 40% of medications were in their normal storage place at the time of the accident. Medicine and bathroom cabinets, and kitchen cupboards and drawers were the safest places to store medications. Handbags, fridges, and shelves or ledges in the bathroom were the most unsafe places. No pack had a low AAI when stored on open shelves indicating that safe packaging cannot compensate for unsafe storage. Other factors which influenced the involvement of medications in accidents were the intended user and the duration of storage. The results of the study have important implications for design of packaging for medications and for education of the public.