1. Respiration during sleep was studied in 16 withdrawn alcoholic patients and in 12 control subjects.
2. The alcoholic patients had increased numbers of central (P < 0.01) and of obstructive (P < 0.05) apnoea and of hypopnoea episodes (P < 0.01) as compared with controls.
3. Significant positive associations were found between the frequencies of central apnoea (P < 0.05) or hypopnoea (P < 0.01) and clinical evidence of central nervous system damage in the alcoholic patients. Hypopnoea also showed a significant association with vagal neuropathy (P < 0.05), assessed by tests of cardioreflexes.
4. We conclude that abnormal respiratory events are common in abstinent alcoholic patients and that they are likely to be at least partly related to nervous damage.