Fatigue lives of adhesive plastics are important due to fatigue lives of constructional glue joints. Epidian 57 composition hardened with triethylenetetramine in two ways: either 7 days at ambient temperature or 1 hour at temp. 60° was the subject of research. Cylindrical samples loaded with harmonic cycles of compressive stresses were tested. Temperature increase caused by variable loading was determined and fatigue lives of plastics were compared dependently on hardening method. The strain of tested material under fatigue loading, dependently on the number of cycles, was measured. An analysis of strain of viscoelastic material under fatigue loading was done. It was demonstrated that the creep at ambient temperature is very important for the process of fatigue failure of the material tested.