Measurements of the ethyl radical -CH2 out-of-plane rocking vibrational fundamental by transient diode laser absorption spectroscopy are reported. The new data provide information on the structure of, and the barrier to internal rotation in, the radical, and how these quantities change on vibrational excitation. We find that the effective barrier decreases from approximately 17 cm(-1) in the zero point level to 10 cm(-1) in the excited vibrational level. The assigned data set now contains approximately 450 rotation-torsional transitions and has been fit to a model effective Hamiltonian. The derived molecular parameters generally reproduce the measured line positions to better than 0.01 cm(-1), but this does not approach the estimated measurement accuracy of 0.001-0.002 cm(-1).