The emission spectrum of RuN has been observed in the near infrared using a Fourier transform spectrometer. RuN molecules were excited in a hollow cathode lamp operated with neon gas and a trace of nitrogen. Two bands with 0-0 Q heads near 7354 and 8079 cm-l and a common lower state have been assigned as (2)Pi(1/2)-(2)Sigma(+) and (2)Pi(3/2)-(2)Sigma(+) subbands, respectively, of a C (2)Pi-X (2)Sigma(+) transition. A rotational analysis of these bands has been performed and molecular constants have been extracted. The principal molecular constants for the ground X (2)Sigma(+) State of the most abundant (RuN)-Ru-102 isotopomer are : B-0 = 0.552 782 9(70) cm(-1) D-0=5.515(13) x 10(-7) cm(-1) gamma(0) = -0.044 432(22) cm(-1) and r(0)=1.573 869(10) Angstrom. The excited C (2)Pi state has the following molecular constants : T-00=7714.342 60(53) cm(-1), A(0)=725.8064(11) cm(-1), B-0 = 0.516 843 4(80) cm(-1), D-0 = 5.685(16) x 10(-7) cm(-1), p(0) = 5.467(36) x 10(-3) cm(-1) and r(0) = 1.627 670(13) Angstrom. Ab initio calculations have been carried out on RuN to ascertain the nature ofthe experimentally observed states and to predict the spectroscopic properties of the low-lying electronic states. Our electronic assignment is supported by these calculations and is also consistent with the observations for the isoelectronic RhC molecule [Kaving and Scullman, J. Mel. Spectrosc. 32, 475-500 (1969)]. The valence electron configuration 1 sigma(2)2 sigma(2)1 pi(4)1 delta(4)3 sigma(1) is proposed for the X (2)Sigma(+) ground state of RuN and the configurations for the excited states have been discussed. There is no previous experimental or theoretical work on RuN;