We report the two photon excitation of CO in the Fourth Positive System, A 1Π ← X 1Σ +, and of N 2 in the Lyman-Birge-Hopfield System, a 1Π g ← x 1Σ + g. In these systems, the S, R, Q, P, and O branches of the 3,0 and 9,0 bands of CO and the 5,0 band of N 2 are excited by radiation of a powerful frequency doubled pulsed dye laser. Doppler free two photon spectra are presented for the S-branch heads of the 9,0 band of CO and the 5,0 band of N 2.