The collisional removal of O-2 molecules prepared in selected vibrational levels of the A (3) Sigma(u)(+) state is studied using a two-laser double-resonance technique. The output of the first laser excites the O-2 to A (3) Sigma(u)(+), nu=6, 7, or 9, and the ultraviolet output of the second laser monitors these levels via resonance-enhanced ionization through either the nu=5 level of the C (3) Pi(g) Rydberg state, or the valence state or states tentatively associated with the 5 (3) Pi(g) state. The temporal evolution of the A (3) Sigma(u)(+) state vibrational level is observed by scanning the time delay between the two pulsed lasers. Collisional removal rate constants are obtained for A (3) Sigma(u)(+), nu=7 and 9 colliding with O-2, N-2, CO2, Ar, and He; and for nu=6 colliding with O-2 and N-2. We find the collisional removal of the A (3) Sigma(u)(+) state to be fast (k greater than or equal to 10(-11) cm(3) s(-1)) for all colliders studied. The rate constants vary by about an order of magnitude from the fastest collisional deactivator, CO2 to the slowest studied, the rare gases Ar and He. The rate constants for the atmospherically important colliders O-2 and N-2 are similar in magnitude and suggest that N-2 collisions will dominate the removal rate in the Earth’s atmosphere.