In EMG recordings of the external anal sphincter there is a brief contraction in response to rapid rectal distension, and a preserved or increased activity during a prolonged substantial rectal distension in healthy adults. In order to determine if this activity develops during childhood 30 healthy children, aged 2 months to 15 years, were examined with their parents' consent. EMG of the external anal sphincter during rest and during rectal distension was performed. All those children who had gained voluntary anal control showed an EMG recording similar to the adults. The 10 youngest children who had not gained voluntary control showed another EMG pattern. Instead of a brief contraction they had a brief loss of activity in response to rectal distension. During a prolonged rectal distension the external sphincter activity decreased and finally ceased. An intermediate state was found in the two youngest children who had gained voluntary control. The EMG pattern showed a good correlation with the maturation and gain of voluntary control of defaecation.