Reproducibility of nocturnal ear oximetry was evaluated in 22 in-patients who were screened for sleep apnoea syndrome. Ohmeda Biox II and Rikadenki printer were applied to each patient during two consecutive nights. The average oxygen desaturation index (ODI) was 6.2 for the first night, and 5.7 for the second night. Intra-individual standard deviation (SD) for ODI was 1.8. Average minimum SpO2 was 86.2% for the first night, and 85.6% for the second night, with an intra-individual SD of 2.1%. If ODI is defined as pathological when five or more, one patient (< 5%) with a pathological result during the first night reached a normal value on the second night, and one patient with a normal result on the first night showed a pathological result on the second night. In conclusion, the results from the first night of ear oximetry do not differ significantly from those of the second night in hospitalised patients with suspected sleep apnoea, provided that the method is appropriately standardised.