Line position data obtained recently for the OH X2Π (12, 8) vibration-rotation band and the B ← X (0, 12) transition are employed in a least-squares analysis to provide the first molecular parameters for the X (v = 12) level. The molecular parameters are estimated using a procedure in which these data are fitted simultaneously in combination with other recent data for the A ← X (4, 2) transition and older data for bands of the C → A and B → A systems. The X (v = 12)Λ-doubling parameters are in excellent agreement with ab initio results. A table of term values is presented for the X2Π (v = 8, 12), A2Σ+ (v = 4-9), B2Σ+ (v = 0, 1), and C2Σ+ (v = 0, 1) levels. © 1991.