The 229 piglets which died on an outdoor unit during a period of eight months were examined post mortem to determine the cause of death. The majority of the deaths (72 per cent) had occurred by the time that the litter was first inspected and of these 27 per cent had uninflated lungs and 53 per cent of the piglets born alive had no food in the stomach. Seventeen per cent of the stillborn pigs were of type I and 83 per cent were of type II. It was impossible to identify stillborn piglets reliably from their external appearance alone. At all ages, crushing was the most common cause of death (72 per cent of liveborn piglets). Six per cent of the corpses of the piglets had been damaged by birds, and attacks on live piglets occurred in the later stages of the study.