The adsorption and desorption kinetics of carbon monoxide from a Pd(110) surface were studied under isothermal conditions using a differentially pumped line of sight mass spectrometer. A number of isothermal adsorption and desorption kinetics were taken by repeating the measurements at different surface temperatures. The sticking probability profiles are fit by the Kisliuk model with initial sticking probability of 0.95. The isothermal desorption rates show nonlinear function of coverage and the apparent desorption rate orders by means of the slope of the van't Hoff plots show unusually high values. The temporal desorption rate curves are discussed in terms of a model which requires the presence of two CO surface phases in equilibrium.