Pre-eclamptic toxaemia (PET) may be associated with both endothelial dysfunction (ED) and sleep-disordered breathing (SDB). It was hypothesised that females with PET would demonstrate both SDB and ED, and that a correlation between these two would suggest a potential causative association.A total of 17 females with PET and 25 matched females with uncomplicated pregnancy were studied. They underwent a nocturnal ambulatory sleep study (using Watch_PAT100) and noninvasive evaluation of endothelial function utilising the reactive hyperaemia test (using Endo_PAT 2000). A higher ratio of post-to pre-occlusion pulse-wave amplitude (endothelial function index (EFI)) indicated better endothelial function.Females with PET had a significantly higher respiratory disturbance index (RDI) and lower EFI than controls (18.4¡8.4 versus 8.3¡1.3?h -1 , and 1.5¡0.1 versus 1.8¡0.1, respectively). Blood pressure significantly correlated with RDI and with EFI. EFI tended to correlate with RDI.In conclusion, these results suggest that both sleep-disordered breathing and endothelial dysfunction are more likely to occur in females with pre-eclamptic toxaemia than in females with uncomplicated pregnancies. The current authors speculate that respiratory disturbances contribute to the functional abnormality of the blood vessels seen in females with pre-eclamptic toxaemia, although causality cannot be determined based on this study.