In the study of 2 + 1 + 1 two-color REMPI spectroscopy of the E(1)Pi(v = 1) <-- D(1)Delta(v = 10) <-- X(1)Sigma(+)(v = 0) transition in CO, the influence of the accidental predissociation in the E1Pi (v = 1) state at j = 9 and 10 was observed, which gives rise to the reduction of line intensity. It is consistent with Ubachs's model of spin-orbit-coupling between E(1)Pi(v = 1) and k(3)Pi(V = 6), which is itself predissociated by a (3)Pi repulsive state. Our experiment also confirmed Baker and Launay's calculation. (C) 2002 Elsevier Science B.V. All rights reserved.