The pattern of postneonatal mortality over the past 16 years in Christchurch and New Zealand is described. In Christchurch the postneonatal rate has risen from about four to eight per 1000 live births over this time, while for the rest of New Zealand the rate has been stable at about six. This rise has been due to an increasing number of cot deaths. The reason for this is unknown. Increased child health surveillance may reduce these deaths.