Results of a satellite observation of the nighttime auroral emission spectrum between 300 and 900 ¿ at 8-¿ resolution are presented. The spectrum was taken from 600-km altitude looking down on a bright, well-defined auroral arc located near the midnight meridian in the north polar region on March 10, 1979, when AE=-500&ggr; (Kp=4). The most prominent features in this wavelength range are identified as the O ii 538-, 617-, 718-, and 834-¿ emisison lines, which have intensities exceeding 50 R. A number of weaker O ii (and possibly N ii and O iii) lines are found widely scattered from 430 to 800 ¿ at intensity levels of ≂10-40 R. As in the dayglow, the measured intensity ratio of the 540 to 585 ¿ features r≥4.1 is discrepant with laboratory measurements of the O ii 538/581-¿ line ratio. Since He i, 537-¿ contamination is probably negligible this result indicates that at least 70% of the observed 540-¿ feature is due to the O ii 2p3 4S0-3s 4P transition multiplets at 539 ¿.