We present a technique for using the measured variations of ultraviolet emissions produced by radiative recombination at 911 and 1356 ¿ to determine the nighttime altitude distribution of F region O+ ions and electrons. The algorithm uses an iterative scheme based on discrete inverse theory to determine the best fit to the data. We present the results of simulations that demonstrate the convergence properties of the algorithm and the fidelity with which it reproduces the input ionosphere. The algorithm was tested against more realistic simulated data generated using the international reference ionosphere (IRI-90) <Bilitza, 1990>. The algorithm accurately retrieved the nighttime F region electron density at midlatitudes (¿25¿--65¿ N) over a wide range of solar and geomagnetic activity and local time.¿ 1997 American Geophysical Union