Describes state-of-the-art procedures for probing bond activation, H-b onded systems, molecular dynamical mechanisms, vibrational dephasing, simple liquids, proteins and energy flow effects using ultrafast vibra tional spectroscopy experiments, as well as discusses experimental and theoretical methods of ultrafast infrared and Raman measurements. Edi ted by the recipient of the American Physical Society's Earl K. Plyler Prize for Molecular Spectroscopy 2000.