In patients with monosymptomatic enuresis we investigated bladder activity together with electroencephalography during sleep on two consecutive nights. Thirty-one patients were investigated. Enuretic episodes were found to be normal micturitions not related to any specific sleep stage. Except for a very few bladder contractions outside the enuresis episode we did not observe any bladder activity. In the few instances where bladder activity was seen it was not associated with changes in EEG activity. The bladder contractions were all eliminated by pelvic floor activity, and this could be seen without any disturbances of the sleep indicating that voiding can be inhibited without the child waking up.