Forms were sent to members of the Obstetric Anaesthetists' Association requesting information on cardiorespiratory disease in pregnancy. Reports of 274 pregnancies in 259 women were received over four years (1997-2000). There were 83 valve lesions, 52 complex congenital heart disease, 112 miscellaneous heart disease and 27 respiratory disease. Half the mothers were classified as New York Heart Association grade I, 29% grade II, 14% grade III, 5% grade IV and six unknown. Thirty-nine mothers were seen by an anaesthetist only just before delivery. Regional analgesia for labour was more likely to be planned for severe (82%) than for mild symptoms (55%; P=0.039), but severity of symptoms did not affect choice of anaesthesia for caesarean section. Eighty-one women were delivered by elective caesarean section, 59 by emergency caesarean section, 82 had spontaneous and 49 assisted vaginal delivery. Three women suffered miscarriages. Regional analgesia was used in 73% of vaginal deliveries, Entonox or pethidine in 15% and no analgesia in 12%. Spinal anaesthesia was used in 21% of caesarean sections, an incremental regional technique (incremental epidural or combined spinal-epidural) in 40% and general anaesthesia in 39%. Forty-three women were admitted to intensive care units electively and 10 unplanned. Ninety-five per cent survived pregnancy in the same state as antepartum, 2% deteriorated and seven died. Ninety-four per cent of babies (258 babies) were delivered in good condition, nine in poor condition and seven died. Despite lack of denominator data and potential biases among the reported cases, the Registry provides a valuable snapshot of current practice in the UK.