The rate coefficient for collisional removal of O-2 (b(1)Sigma(g)(+), nu = 1) by O(P-3), k(O), is an essential parameter in modeling the emissions from O-2(b(1)Sigma(g)(+), nu = 1) in the Earth's thermosphere. We report a laboratory measurement of this rate coefficient at room temperature. A fluorine laser is used to photodissociate O-2 at 157.6 nm, followed by detection of the time-resolved fluorescence from subsequently generated O-2 (b(1)Sigma(g)(+), nu = 1). The determined value is k(O) = 4.5(-1.3)(+0.8) x 10(-12) cm(3) s(-1) (2sigma). The rate coefficient for collisional removal of O-2 (b(1)Sigma(g)(+), nu = 1) by O-2 is also determined, with a value of (1.5 +/- 0.1) x 10(-11) cm(3) s(-1). (C) 2005 Elsevier B.V. All rights reserved.