Twenty five laser lines in water vapor are identified as transitions between known vibration‐rotation levels. The mechanism is discussed: The initiating factor is a weak perturbation involving close resonance between levels of the bending overtone and the stretching fundamentals. Three resonances account for most of the strongest lines: 020, 550↔ 100, 514, at 4050 cm−1, 020, 661↔ 001, 633, at 4408 cm−1, and 020, 844↔ 100, 808at 4387 cm−1above the zero level. The 2527952.8 MHz line is assigned to 001, 642→ 020, 661.