In a prospective study we tested the hypothesis that a cry from an infant can be used as part of an instrument to measure pain. Ten healthy newly born infants were subjected to painful stimuli on four occasions during their first year of life. The sound of the crying was analysed with regard to duration. With the help of a sound spectrogram, the fundamental frequencies of the first five crying sounds were analysed. The number of crying sounds decreased with age. There was a considerable difference between the 10 children, and also between the different pricking occasions for the respective children. We conclude that if crying is to be used as part of an instrument for measuring pain, the child's age has to be taken into account.