The crack layer theory has been well established as a good description of the energy dependence of fatigue crack propagation in thermoplastics associated with multiple crazes or large deformation preceding the crack tip. Since PMMA usually displays crack propagation preceded by a single craze, the applicability of the theory in such extreme cases needs to be tested. Fatigue crack propagation data obtained in a previous interferometric investigation in PMMA have been utilized here. Two different approaches are attempted for estimation of the energy dissipated in craze formation and growth. Using both approaches, the crack layer formalism provides a reasonably good description of the crack propagation behavior in PMMA.